24 files changed, 2149 insertions, 1228 deletions

diff --git a/contrib/tzdata/CONTRIBUTING b/contrib/tzdata/CONTRIBUTING
index 22addd2b546f..716f32b3a39a 100644
--- a/contrib/tzdata/CONTRIBUTING
+++ b/contrib/tzdata/CONTRIBUTING
@@ -5,20 +5,26 @@ change timekeeping rules erratically and sometimes with little
 warning, the data entries do not cover all of civil time before
 1970, and undoubtedly errors remain in the code and data.  Feel
 free to fill gaps or fix mistakes, and please email improvements
-to tz@iana.org for use in the future.
+to tz@iana.org for use in the future.  In your email, please give
+reliable sources that reviewers can check.
+
+-----
+
+Developers can contribute technical changes to the source code and
+data as follows.
 
 To email small changes, please run a POSIX shell command like
 'diff -u old/europe new/europe >myfix.patch', and attach
 myfix.patch to the email.
 
-For more-elaborate changes, please read the Theory file and browse
-the mailing list archives <http://mm.icann.org/pipermail/tz/> for
-examples of patches that tend to work well.  Ideally, additions to
+For more-elaborate changes, please read the theory.html file and browse
+the mailing list archives <https://mm.icann.org/pipermail/tz/> for
+examples of patches that tend to work well.  Additions to
 data should contain commentary citing reliable sources as
-justification.
+justification.  Citations should use https: URLs if available.
 
 Please submit changes against either the latest release in
-<ftp://ftp.iana.org/tz/> or the master branch of the development
+<https://www.iana.org/time-zones> or the master branch of the development
 repository.  If you use Git the following workflow may be helpful:
 
   * Copy the development repository.
diff --git a/contrib/tzdata/LICENSE b/contrib/tzdata/LICENSE
index 148eb232b673..8ba4399c622d 100644
--- a/contrib/tzdata/LICENSE
+++ b/contrib/tzdata/LICENSE
@@ -1,4 +1,5 @@
-With a few exceptions, all files in the tz code and data (including
-this one) are in the public domain.  The exceptions are date.c,
-newstrftime.3, and strftime.c, which contain material derived from BSD
-and which use the BSD 3-clause license.
+Unless specified below, all files in the tz code and data (including
+this LICENSE file) are in the public domain.
+
+If the files date.c, newstrftime.3, and strftime.c are present, they
+contain material derived from BSD and use the BSD 3-clause license.
diff --git a/contrib/tzdata/Makefile b/contrib/tzdata/Makefile
index 8067ba087b43..c92edc064084 100644
--- a/contrib/tzdata/Makefile
+++ b/contrib/tzdata/Makefile
@@ -49,6 +49,7 @@ TOPDIR=		/usr/local
 # "Compiled" time zone information is placed in the "TZDIR" directory
 # (and subdirectories).
 # Use an absolute path name for TZDIR unless you're just testing the software.
+# TZDIR_BASENAME should not contain "/" and should not be ".", ".." or empty.
 
 TZDIR_BASENAME=	zoneinfo
 TZDIR=		$(TOPDIR)/etc/$(TZDIR_BASENAME)
@@ -75,7 +76,7 @@ LIBDIR=		$(TOPDIR)/lib
 # If you want only POSIX time, with time values interpreted as
 # seconds since the epoch (not counting leap seconds), use
 #	REDO=		posix_only
-# below.  If you want want only "right" time, with values interpreted
+# below.  If you want only "right" time, with values interpreted
 # as seconds since the epoch (counting leap seconds), use
 #	REDO=		right_only
 # below.  If you want both sets of data available, with leap seconds not
@@ -92,6 +93,24 @@ LIBDIR=		$(TOPDIR)/lib
 
 REDO=		posix_right
 
+# To install data in text form that has all the information of the binary data,
+# (optionally incorporating leap second information), use
+#	TZDATA_TEXT=	tzdata.zi leapseconds
+# To install text data without leap second information (e.g., because
+# REDO='posix_only'), use
+#	TZDATA_TEXT=	tzdata.zi
+# To avoid installing text data, use
+#	TZDATA_TEXT=
+
+TZDATA_TEXT=	leapseconds tzdata.zi
+
+# For backward-compatibility links for old zone names, use
+#	BACKWARD=	backward pacificnew
+# To omit these links, use
+#	BACKWARD=
+
+BACKWARD=	backward pacificnew
+
 # If you want out-of-scope and often-wrong data from the file 'backzone', use
 #	PACKRATDATA=	backzone
 # To omit this data, use
@@ -99,6 +118,11 @@ REDO=		posix_right
 
 PACKRATDATA=
 
+# The name of a locale using the UTF-8 encoding, used during self-tests.
+# The tests are skipped if the name does not appear to work on this system.
+
+UTF8_LOCALE=	en_US.utf8
+
 # Since "." may not be in PATH...
 
 YEARISTYPE=	./yearistype
@@ -106,50 +130,53 @@ YEARISTYPE=	./yearistype
 # Non-default libraries needed to link.
 LDLIBS=
 
-# Add the following to the end of the "CFLAGS=" line as needed.
+# Add the following to the end of the "CFLAGS=" line as needed to override
+# defaults specified in the source code.  "-DFOO" is equivalent to "-DFOO=1".
 #  -DBIG_BANG=-9999999LL if the Big Bang occurred at time -9999999 (see zic.c)
+#  -DDEPRECATE_TWO_DIGIT_YEARS for optional runtime warnings about strftime
+#	formats that generate only the last two digits of year numbers
+#  -DEPOCH_LOCAL if the 'time' function returns local time not UT
+#  -DEPOCH_OFFSET=N if the 'time' function returns a value N greater
+#	than what POSIX specifies, assuming local time is UT.
+#	For example, N is 252460800 on AmigaOS.
 #  -DHAVE_DECL_ASCTIME_R=0 if <time.h> does not declare asctime_r
+#  -DHAVE_DECL_ENVIRON if <unistd.h> declares 'environ'
 #  -DHAVE_DIRECT_H if mkdir needs <direct.h> (MS-Windows)
-#  -DHAVE_DOS_FILE_NAMES if file names have drive specifiers etc. (MS-DOS)
-#  -DHAVE_GETTEXT=1 if 'gettext' works (e.g., GNU/Linux, FreeBSD, Solaris)
-#  -DHAVE_INCOMPATIBLE_CTIME_R=1 if your system's time.h declares
+#  -DHAVE_GENERIC=0 if _Generic does not work
+#  -DHAVE_GETTEXT if 'gettext' works (e.g., GNU/Linux, FreeBSD, Solaris)
+#  -DHAVE_INCOMPATIBLE_CTIME_R if your system's time.h declares
 #	ctime_r and asctime_r incompatibly with the POSIX standard
 #	(Solaris when _POSIX_PTHREAD_SEMANTICS is not defined).
-#  -DHAVE_INTTYPES_H=1 if you have a pre-C99 compiler with "inttypes.h"
+#  -DHAVE_INTTYPES_H if you have a non-C99 compiler with <inttypes.h>
 #  -DHAVE_LINK=0 if your system lacks a link function
 #  -DHAVE_LOCALTIME_R=0 if your system lacks a localtime_r function
 #  -DHAVE_LOCALTIME_RZ=0 if you do not want zdump to use localtime_rz
-#	This defaults to 1 if a working localtime_rz seems to be available.
 #	localtime_rz can make zdump significantly faster, but is nonstandard.
 #  -DHAVE_POSIX_DECLS=0 if your system's include files do not declare
 #	functions like 'link' or variables like 'tzname' required by POSIX
-#  -DHAVE_STDINT_H=1 if you have a pre-C99 compiler with "stdint.h"
-#  -DHAVE_STRFTIME_L=1 if <time.h> declares locale_t and strftime_l
-#	This defaults to 0 if _POSIX_VERSION < 200809, 1 otherwise.
+#  -DHAVE_SNPRINTF=0 if your system lacks the snprintf function
+#  -DHAVE_STDBOOL_H if you have a non-C99 compiler with <stdbool.h>
+#  -DHAVE_STDINT_H if you have a non-C99 compiler with <stdint.h>
+#  -DHAVE_STRFTIME_L if <time.h> declares locale_t and strftime_l
 #  -DHAVE_STRDUP=0 if your system lacks the strdup function
 #  -DHAVE_SYMLINK=0 if your system lacks the symlink function
-#  -DHAVE_SYS_STAT_H=0 if your compiler lacks a "sys/stat.h"
-#  -DHAVE_SYS_WAIT_H=0 if your compiler lacks a "sys/wait.h"
+#  -DHAVE_SYS_STAT_H=0 if your compiler lacks a <sys/stat.h>
+#  -DHAVE_SYS_WAIT_H=0 if your compiler lacks a <sys/wait.h>
 #  -DHAVE_TZSET=0 if your system lacks a tzset function
-#  -DHAVE_UNISTD_H=0 if your compiler lacks a "unistd.h" (Microsoft C++ 7?)
-#  -DEPOCH_LOCAL=1 if the 'time' function returns local time not UT
-#  -DEPOCH_OFFSET=N if the 'time' function returns a value N greater
-#	than what POSIX specifies, assuming local time is UT.
-#	For example, N is 252460800 on AmigaOS.
-#  -DNO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU=1
-#	if you do not want run time warnings about formats that may cause
-#	year 2000 grief
-#  -Dssize_t=long on ancient hosts that lack ssize_t
-#  -DTHREAD_SAFE=1 to make localtime.c thread-safe, as POSIX requires;
+#  -DHAVE_UNISTD_H=0 if your compiler lacks a <unistd.h>
+#  -Dlocale_t=XXX if your system uses XXX instead of locale_t
+#  -Dssize_t=long on hosts like MS-Windows that lack ssize_t
+#  -DTHREAD_SAFE to make localtime.c thread-safe, as POSIX requires;
 #	not needed by the main-program tz code, which is single-threaded.
 #	Append other compiler flags as needed, e.g., -pthread on GNU/Linux.
 #  -Dtime_tz=\"T\" to use T as the time_t type, rather than the system time_t
+#	This is intended for internal use only; it mangles external names.
 #  -DTZ_DOMAIN=\"foo\" to use "foo" for gettext domain name; default is "tz"
 #  -DTZ_DOMAINDIR=\"/path\" to use "/path" for gettext directory;
 #	the default is system-supplied, typically "/usr/lib/locale"
 #  -DTZDEFRULESTRING=\",date/time,date/time\" to default to the specified
 #	DST transitions if the time zone files cannot be accessed
-#  -DUNINIT_TRAP=1 if reading uninitialized storage can cause problems
+#  -DUNINIT_TRAP if reading uninitialized storage can cause problems
 #	other than simply getting garbage data
 #  -DUSE_LTZ=0 to build zdump with the system time zone library
 #	Also set TZDOBJS=zdump.o and CHECK_TIME_T_ALTERNATIVES= below.
@@ -157,26 +184,27 @@ LDLIBS=
 #	(or some other number) to set the maximum time zone abbreviation length
 #	that zic will accept without a warning (the default is 6)
 #  $(GCC_DEBUG_FLAGS) if you are using recent GCC and want lots of checking
-GCC_DEBUG_FLAGS = -Dlint -g3 -O3 -fno-common -fstrict-aliasing \
-	-Wall -Wextra \
-	-Wbad-function-cast -Wcast-align -Wdate-time \
-	-Wdeclaration-after-statement \
-	-Wdouble-promotion \
-	-Wformat=2 -Winit-self -Wjump-misses-init \
-	-Wlogical-op -Wmissing-prototypes -Wnested-externs \
-	-Wold-style-definition -Woverlength-strings -Wpointer-arith \
-	-Wshadow -Wstrict-prototypes -Wsuggest-attribute=const \
-	-Wsuggest-attribute=format -Wsuggest-attribute=noreturn \
-	-Wsuggest-attribute=pure -Wtrampolines \
-	-Wundef -Wunused -Wwrite-strings \
-	-Wno-address -Wno-format-nonliteral -Wno-sign-compare \
-	-Wno-type-limits -Wno-unused-parameter
-#
-# If you want to use System V compatibility code, add
-#	-DUSG_COMPAT
-# to the end of the "CFLAGS=" line.  This arrange for "timezone" and "daylight"
-# variables to be kept up-to-date by the time conversion functions.  Neither
-# "timezone" nor "daylight" is described in X3J11's work.
+# Select instrumentation via "make GCC_INSTRUMENT='whatever'".
+GCC_INSTRUMENT = \
+  -fsanitize=undefined -fsanitize-address-use-after-scope \
+  -fsanitize-undefined-trap-on-error -fstack-protector
+GCC_DEBUG_FLAGS = -DGCC_LINT -g3 -O3 -fno-common \
+  $(GCC_INSTRUMENT) \
+  -Wall -Wextra \
+  -Walloc-size-larger-than=100000 -Warray-bounds=2 \
+  -Wbad-function-cast -Wcast-align -Wdate-time \
+  -Wdeclaration-after-statement -Wdouble-promotion \
+  -Wformat=2 -Wformat-overflow=2 -Wformat-signedness -Wformat-truncation \
+  -Winit-self -Wjump-misses-init -Wlogical-op \
+  -Wmissing-declarations -Wmissing-prototypes -Wnested-externs \
+  -Wold-style-definition -Woverlength-strings -Wpointer-arith \
+  -Wshadow -Wshift-overflow=2 -Wstrict-prototypes -Wstringop-overflow=5 \
+  -Wsuggest-attribute=const -Wsuggest-attribute=format \
+  -Wsuggest-attribute=noreturn -Wsuggest-attribute=pure \
+  -Wtrampolines -Wundef -Wuninitialized -Wunused \
+  -Wvariadic-macros -Wvla -Wwrite-strings \
+  -Wno-address -Wno-format-nonliteral -Wno-sign-compare \
+  -Wno-type-limits -Wno-unused-parameter
 #
 # If your system has a "GMT offset" field in its "struct tm"s
 # (or if you decide to add such a field in your system's "time.h" file),
@@ -189,6 +217,31 @@ GCC_DEBUG_FLAGS = -Dlint -g3 -O3 -fno-common -fstrict-aliasing \
 # and define NO_TM_ZONE to suppress any guessing.  These two fields are not
 # required by POSIX, but are widely available on GNU/Linux and BSD systems.
 #
+# The next batch of options control support for external variables
+# exported by tzcode.  In practice these variables are less useful
+# than TM_GMTOFF and TM_ZONE.  However, most of them are standardized.
+# #
+# # To omit or support the external variable "tzname", add one of:
+# #	-DHAVE_TZNAME=0
+# #	-DHAVE_TZNAME=1
+# # to the "CFLAGS=" line.  "tzname" is required by POSIX 1988 and later.
+# # If not defined, the code attempts to guess HAVE_TZNAME from other macros.
+# # Warning: unless time_tz is also defined, HAVE_TZNAME=1 can cause
+# # crashes when combined with some platforms' standard libraries,
+# # presumably due to memory allocation issues.
+# #
+# # To omit or support the external variables "timezone" and "daylight", add
+# #	-DUSG_COMPAT=0
+# #	-DUSG_COMPAT=1
+# # to the "CFLAGS=" line; "timezone" and "daylight" are inspired by
+# # Unix Systems Group code and are required by POSIX 2008 (with XSI) and later.
+# # If not defined, the code attempts to guess USG_COMPAT from other macros.
+# #
+# # To support the external variable "altzone", add
+# #	-DALTZONE
+# # to the end of the "CFLAGS=" line; although "altzone" appeared in
+# # System V Release 3.1 it has not been standardized.
+#
 # If you want functions that were inspired by early versions of X3J11's work,
 # add
 #	-DSTD_INSPIRED
@@ -226,11 +279,6 @@ GCC_DEBUG_FLAGS = -Dlint -g3 -O3 -fno-common -fstrict-aliasing \
 #	-DALL_STATE
 # to the end of the "CFLAGS=" line.  Storage is obtained by calling malloc.
 #
-# If you want an "altzone" variable (a la System V Release 3.1), add
-#	-DALTZONE
-# to the end of the "CFLAGS=" line.
-# This variable is not described in X3J11's work.
-#
 # NIST-PCTS:151-2, Version 1.4, (1993-12-03) is a test suite put
 # out by the National Institute of Standards and Technology
 # which claims to test C and Posix conformance.  If you want to pass PCTS, add
@@ -240,8 +288,8 @@ GCC_DEBUG_FLAGS = -Dlint -g3 -O3 -fno-common -fstrict-aliasing \
 # If you want strict compliance with XPG4 as of 1994-04-09, add
 #	-DXPG4_1994_04_09
 # to the end of the "CFLAGS=" line.  This causes "strftime" to always return
-# 53 as a week number (rather than 52 or 53) for those days in January that
-# before the first Monday in January when a "%V" format is used and January 1
+# 53 as a week number (rather than 52 or 53) for January days before
+# January's first Monday when a "%V" format is used and January 1
 # falls on a Friday, Saturday, or Sunday.
 
 CFLAGS=
@@ -265,7 +313,7 @@ ZFLAGS=
 
 # How to use zic to install tz binary files.
 
-ZIC_INSTALL=	$(ZIC) -y $(YEARISTYPE) -d $(DESTDIR)$(TZDIR) $(LEAPSECONDS)
+ZIC_INSTALL=	$(ZIC) -d $(DESTDIR)$(TZDIR) $(LEAPSECONDS)
 
 # The name of a Posix-compliant 'awk' on your system.
 AWK=		awk
@@ -289,6 +337,7 @@ SGML_CATALOG_FILES= \
 # The name, arguments and environment of a program to validate your web pages.
 # See <http://openjade.sourceforge.net/doc/> for a validator, and
 # <https://validator.w3.org/source/> for a validation library.
+# Set VALIDATE=':' if you do not have such a program.
 VALIDATE = nsgmls
 VALIDATE_FLAGS = -s -B -wall -wno-unused-param
 VALIDATE_ENV = \
@@ -355,7 +404,7 @@ AR=		ar
 RANLIB=		:
 
 TZCOBJS=	zic.o
-TZDOBJS=	zdump.o localtime.o asctime.o
+TZDOBJS=	zdump.o localtime.o asctime.o strftime.o
 DATEOBJS=	date.o localtime.o strftime.o asctime.o
 LIBSRCS=	localtime.c asctime.c difftime.c
 LIBOBJS=	localtime.o asctime.o difftime.o
@@ -370,33 +419,35 @@ MANTXTS=	newctime.3.txt newstrftime.3.txt newtzset.3.txt \
 			time2posix.3.txt \
 			tzfile.5.txt tzselect.8.txt zic.8.txt zdump.8.txt \
 			date.1.txt
-COMMON=		CONTRIBUTING LICENSE Makefile NEWS README Theory version
+COMMON=		calendars CONTRIBUTING LICENSE Makefile \
+			NEWS README theory.html version
 WEB_PAGES=	tz-art.htm tz-how-to.html tz-link.htm
 DOCS=		$(MANS) date.1 $(MANTXTS) $(WEB_PAGES)
 PRIMARY_YDATA=	africa antarctica asia australasia \
 		europe northamerica southamerica
-YDATA=		$(PRIMARY_YDATA) pacificnew etcetera backward
+YDATA=		$(PRIMARY_YDATA) etcetera $(BACKWARD)
 NDATA=		systemv factory
 TDATA=		$(YDATA) $(NDATA)
 ZONETABLES=	zone1970.tab zone.tab
-TABDATA=	iso3166.tab leapseconds $(ZONETABLES)
+TABDATA=	iso3166.tab $(TZDATA_TEXT) $(ZONETABLES)
 LEAP_DEPS=	leapseconds.awk leap-seconds.list
-DATA=		$(YDATA) $(NDATA) backzone $(TABDATA) \
-			leap-seconds.list yearistype.sh
-AWK_SCRIPTS=	checklinks.awk checktab.awk leapseconds.awk
+TZDATA_ZI_DEPS=	zishrink.awk $(TDATA) $(PACKRATDATA)
+DATA=		$(YDATA) $(NDATA) backzone iso3166.tab leap-seconds.list \
+			leapseconds yearistype.sh $(ZONETABLES)
+AWK_SCRIPTS=	checklinks.awk checktab.awk leapseconds.awk zishrink.awk
 MISC=		$(AWK_SCRIPTS) zoneinfo2tdf.pl
 TZS_YEAR=	2050
 TZS=		to$(TZS_YEAR).tzs
 TZS_NEW=	to$(TZS_YEAR)new.tzs
 TZS_DEPS=	$(PRIMARY_YDATA) asctime.c localtime.c \
 			private.h tzfile.h zdump.c zic.c
-ENCHILADA=	$(COMMON) $(DOCS) $(SOURCES) $(DATA) $(MISC) $(TZS)
+ENCHILADA=	$(COMMON) $(DOCS) $(SOURCES) $(DATA) $(MISC) $(TZS) tzdata.zi
 
 # Consult these files when deciding whether to rebuild the 'version' file.
 # This list is not the same as the output of 'git ls-files', since
 # .gitignore is not distributed.
 VERSION_DEPS= \
-		CONTRIBUTING LICENSE Makefile NEWS README Theory \
+		calendars CONTRIBUTING LICENSE Makefile NEWS README \
 		africa antarctica asctime.c asia australasia \
 		backward backzone \
 		checklinks.awk checktab.awk \
@@ -405,7 +456,7 @@ VERSION_DEPS= \
 		leap-seconds.list leapseconds.awk localtime.c \
 		newctime.3 newstrftime.3 newtzset.3 northamerica \
 		pacificnew private.h \
-		southamerica strftime.c systemv \
+		southamerica strftime.c systemv theory.html \
 		time2posix.3 tz-art.htm tz-how-to.html tz-link.htm \
 		tzfile.5 tzfile.h tzselect.8 tzselect.ksh \
 		workman.sh yearistype.sh \
@@ -427,7 +478,7 @@ install:	all $(DATA) $(REDO) $(MANS)
 			$(DESTDIR)$(MANDIR)/man3 $(DESTDIR)$(MANDIR)/man5 \
 			$(DESTDIR)$(MANDIR)/man8
 		$(ZIC_INSTALL) -l $(LOCALTIME) -p $(POSIXRULES)
-		cp -f iso3166.tab $(ZONETABLES) $(DESTDIR)$(TZDIR)/.
+		cp -f $(TABDATA) $(DESTDIR)$(TZDIR)/.
 		cp tzselect zic zdump $(DESTDIR)$(ETCDIR)/.
 		cp libtz.a $(DESTDIR)$(LIBDIR)/.
 		$(RANLIB) $(DESTDIR)$(LIBDIR)/libtz.a
@@ -448,6 +499,11 @@ version:	$(VERSION_DEPS)
 		printf '%s\n' "$$V" >$@.out
 		mv $@.out $@
 
+# This file can be tailored by setting BACKWARD, PACKRATDATA, etc.
+tzdata.zi:	$(TZDATA_ZI_DEPS)
+		LC_ALL=C $(AWK) -f zishrink.awk $(TDATA) $(PACKRATDATA) >$@.out
+		mv $@.out $@
+
 version.h:	version
 		VERSION=`cat version` && printf '%s\n' \
 		  'static char const PKGVERSION[]="($(PACKAGE)) ";' \
@@ -473,6 +529,7 @@ leapseconds:	$(LEAP_DEPS)
 # Arguments to pass to submakes of install_data.
 # They can be overridden by later submake arguments.
 INSTALLARGS = \
+ BACKWARD=$(BACKWARD) \
  DESTDIR=$(DESTDIR) \
  LEAPSECONDS='$(LEAPSECONDS)' \
  PACKRATDATA='$(PACKRATDATA)' \
@@ -481,10 +538,8 @@ INSTALLARGS = \
  ZIC='$(ZIC)'
 
 # 'make install_data' installs one set of tz binary files.
-# It can be tailored by setting LEAPSECONDS, PACKRATDATA, etc.
-install_data:	zic leapseconds yearistype $(PACKRATDATA) $(TDATA)
-		$(ZIC_INSTALL) $(TDATA)
-		$(AWK) '/^Rule/' $(TDATA) | $(ZIC_INSTALL) - $(PACKRATDATA)
+install_data:	zic leapseconds yearistype tzdata.zi
+		$(ZIC_INSTALL) tzdata.zi
 
 posix_only:
 		$(MAKE) $(INSTALLARGS) LEAPSECONDS= install_data
@@ -521,14 +576,14 @@ posix_packrat:
 
 zones:		$(REDO)
 
-$(TZS_NEW):	$(TDATA) zdump zic
+$(TZS_NEW):	tzdata.zi zdump zic
 		mkdir -p tzs.dir
-		$(zic) -d tzs.dir $(TDATA)
-		$(AWK) '/^Link/{print $$1 "\t" $$2 "\t" $$3}' \
-		   $(TDATA) | LC_ALL=C sort >$@.out
+		$(zic) -d tzs.dir tzdata.zi
+		$(AWK) '/^L/{print "Link\t" $$2 "\t" $$3}' \
+		   tzdata.zi | LC_ALL=C sort >$@.out
 		wd=`pwd` && \
 		zones=`$(AWK) -v wd="$$wd" \
-				'/^Zone/{print wd "/tzs.dir/" $$2}' $(TDATA) \
+				'/^Z/{print wd "/tzs.dir/" $$2}' tzdata.zi \
 			 | LC_ALL=C sort` && \
 		./zdump -i -c $(TZS_YEAR) $$zones >>$@.out
 		sed 's,^TZ=".*tzs\.dir/,TZ=",' $@.out >$@.sed.out
@@ -564,24 +619,37 @@ tzselect:	tzselect.ksh version
 		chmod +x $@.out
 		mv $@.out $@
 
-check:		check_character_set check_white_space check_links check_sorted \
-		  check_tables check_tzs check_web
+check:		check_character_set check_white_space check_links \
+		  check_name_lengths check_sorted \
+		  check_tables check_web check_zishrink check_tzs
 
 check_character_set: $(ENCHILADA)
-		LC_ALL=en_US.utf8 && export LC_ALL && \
+	test ! '$(UTF8_LOCALE)' || \
+	! printf 'A\304\200B\n' | \
+	  LC_ALL='$(UTF8_LOCALE)' grep -q '^A.B$$' >/dev/null 2>&1 || { \
+		LC_ALL='$(UTF8_LOCALE)' && export LC_ALL && \
 		sharp='#' && \
 		! grep -Env $(SAFE_LINE) $(MANS) date.1 $(MANTXTS) \
 			$(MISC) $(SOURCES) $(WEB_PAGES) \
-			CONTRIBUTING LICENSE Makefile README version && \
+			CONTRIBUTING LICENSE Makefile README \
+			version tzdata.zi && \
 		! grep -Env $(SAFE_SHARP_LINE) $(TDATA) backzone \
 			leapseconds yearistype.sh zone.tab && \
-		! grep -Env $(OK_LINE) $(ENCHILADA)
+		! grep -Env $(OK_LINE) $(ENCHILADA); \
+	}
 
 check_white_space: $(ENCHILADA)
 		patfmt=' \t|[\f\r\v]' && pat=`printf "$$patfmt\\n"` && \
 		! grep -En "$$pat" $(ENCHILADA)
 		! grep -n '[[:space:]]$$' $(ENCHILADA)
 
+PRECEDES_FILE_NAME = ^(Zone|Link[[:space:]]+[^[:space:]]+)[[:space:]]+
+FILE_NAME_COMPONENT_TOO_LONG = \
+  $(PRECEDES_FILE_NAME)[^[:space:]]*[^/[:space:]]{15}
+
+check_name_lengths: $(TDATA) backzone
+		! grep -En '$(FILE_NAME_COMPONENT_TOO_LONG)' $(TDATA) backzone
+
 CHECK_CC_LIST = { n = split($$1,a,/,/); for (i=2; i<=n; i++) print a[1], a[i]; }
 
 check_sorted: backward backzone iso3166.tab zone.tab zone1970.tab
@@ -596,6 +664,7 @@ check_sorted: backward backzone iso3166.tab zone.tab zone1970.tab
 
 check_links:	checklinks.awk $(TDATA)
 		$(AWK) -f checklinks.awk $(TDATA)
+		$(AWK) -f checklinks.awk tzdata.zi
 
 check_tables:	checktab.awk $(PRIMARY_YDATA) $(ZONETABLES)
 		for tab in $(ZONETABLES); do \
@@ -606,14 +675,32 @@ check_tables:	checktab.awk $(PRIMARY_YDATA) $(ZONETABLES)
 check_tzs:	$(TZS) $(TZS_NEW)
 		diff -u $(TZS) $(TZS_NEW)
 
-check_web:	$(WEB_PAGES)
-		$(VALIDATE_ENV) $(VALIDATE) $(VALIDATE_FLAGS) $(WEB_PAGES)
+# This checks only the HTML 4.01 strict page.
+# To check the the other pages, use <https://validator.w3.org/>.
+check_web:	tz-how-to.html
+		$(VALIDATE_ENV) $(VALIDATE) $(VALIDATE_FLAGS) tz-how-to.html
+
+# Check that tzdata.zi generates the same binary data that its sources do.
+check_zishrink: tzdata.zi zic leapseconds $(PACKRATDATA) $(TDATA)
+		for type in posix right; do \
+		  mkdir -p time_t.dir/$$type time_t.dir/$$type-shrunk && \
+		  case $$type in \
+		    right) leap='-L leapseconds';; \
+	            *) leap=;; \
+		  esac && \
+		  $(ZIC) $$leap -d time_t.dir/$$type $(TDATA) && \
+		  $(AWK) '/^Rule/' $(TDATA) | \
+		    $(ZIC) $$leap -d time_t.dir/$$type - $(PACKRATDATA) && \
+		  $(ZIC) $$leap -d time_t.dir/$$type-shrunk tzdata.zi && \
+		  diff -r time_t.dir/$$type time_t.dir/$$type-shrunk || exit; \
+		done
+		rm -fr time_t.dir
 
 clean_misc:
 		rm -f core *.o *.out \
 		  date tzselect version.h zdump zic yearistype libtz.a
 clean:		clean_misc
-		rm -fr *.dir tzdb-*/ $(TZS_NEW)
+		rm -fr *.dir tzdata.zi tzdb-*/ $(TZS_NEW)
 
 maintainer-clean: clean
 		@echo 'This command is intended for maintainers to use; it'
@@ -667,6 +754,7 @@ set-timestamps.out: $(ENCHILADA)
 		  touch -cmr `ls -t $$file workman.sh | sed 1q` $$file.txt || \
 		    exit; \
 		done
+		touch -cmr `ls -t $(TZDATA_ZI_DEPS) | sed 1q` tzdata.zi
 		touch -cmr `ls -t $(TZS_DEPS) | sed 1q` $(TZS)
 		touch -cmr `ls -t $(VERSION_DEPS) | sed 1q` version
 		touch $@
@@ -678,7 +766,7 @@ check_public:
 		$(MAKE) maintainer-clean
 		$(MAKE) "CFLAGS=$(GCC_DEBUG_FLAGS)" ALL
 		mkdir -p public.dir
-		for i in $(TDATA) ; do \
+		for i in $(TDATA) tzdata.zi; do \
 		  $(zic) -v -d public.dir $$i 2>&1 || exit; \
 		done
 		$(zic) -v -d public.dir $(TDATA)
@@ -772,8 +860,8 @@ typecheck:
 			$(MAKE) clean ; \
 		done
 
-zonenames:	$(TDATA)
-		@$(AWK) '/^Zone/ { print $$2 } /^Link/ { print $$3 }' $(TDATA)
+zonenames:	tzdata.zi
+		@$(AWK) '/^Z/ { print $$2 } /^L/ { print $$3 }' tzdata.zi
 
 asctime.o:	private.h tzfile.h
 date.o:		private.h
@@ -789,6 +877,7 @@ zic.o:		private.h tzfile.h version.h
 .PHONY: check check_character_set check_links
 .PHONY: check_public check_sorted check_tables
 .PHONY: check_time_t_alternatives check_tzs check_web check_white_space
+.PHONY: check_zishrink
 .PHONY: clean clean_misc force_tzs
 .PHONY: install install_data maintainer-clean names
 .PHONY: posix_only posix_packrat posix_right
diff --git a/contrib/tzdata/NEWS b/contrib/tzdata/NEWS
index f986cf6f0f67..bd2bec223a0b 100644
--- a/contrib/tzdata/NEWS
+++ b/contrib/tzdata/NEWS
@@ -1,5 +1,169 @@
 News for the tz database
 
+Release 2017c - 2017-10-20 14:49:34 -0700
+
+  Briefly:
+  Northern Cyprus switches from +03 to +02/+03 on 2017-10-29.
+  Fiji ends DST 2018-01-14, not 2018-01-21.
+  Namibia switches from +01/+02 to +02 on 2018-04-01.
+  Sudan switches from +03 to +02 on 2017-11-01.
+  Tonga likely switches from +13/+14 to +13 on 2017-11-05.
+  Turks & Caicos switches from -04 to -05/-04 on 2018-11-04.
+  A new file tzdata.zi now holds a small text copy of all data.
+  The zic input format has been regularized slightly.
+
+  Changes to future time stamps
+
+    Northern Cyprus has decided to resume EU rules starting
+    2017-10-29, thus reinstituting winter time.
+
+    Fiji ends DST 2018-01-14 instead of the 2018-01-21 previously
+    predicted.  (Thanks to Dominic Fok.)  Adjust future predictions
+    accordingly.
+
+    Namibia will switch from +01 with DST to +02 all year on
+    2017-09-03 at 02:00.  This affects UT offsets starting 2018-04-01
+    at 02:00.  (Thanks to Steffen Thorsen.)
+
+    Sudan will switch from +03 to +02 on 2017-11-01.  (Thanks to Ahmed
+    Atyya and Yahia Abdalla.)  South Sudan is not switching, so
+    Africa/Juba is no longer a link to Africa/Khartoum.
+
+    Tonga has likely ended its experiment with DST, and will not
+    adjust its clocks on 2017-11-05.  Although Tonga has not announced
+    whether it will continue to observe DST, the IATA is assuming that
+    it will not.  (Thanks to David Wade.)
+
+    Turks & Caicos will switch from -04 all year to -05 with US DST on
+    2018-03-11 at 03:00.  This affects UT offsets starting 2018-11-04
+    at 02:00.  (Thanks to Steffen Thorsen.)
+
+  Changes to past time stamps
+
+    Namibia switched from +02 to +01 on 1994-03-21, not 1994-04-03.
+    (Thanks to Arthur David Olson.)
+
+    Detroit did not observe DST in 1967.
+
+    Use railway time for Asia/Kolkata before 1941, by switching to
+    Madras local time (UT +052110) in 1870, then to IST (UT +0530) in
+    1906.  Also, treat 1941-2's +0630 as DST, like 1942-5.
+
+    Europe/Dublin's 1946 and 1947 fallback transitions occurred at
+    02:00 standard time, not 02:00 DST.  (Thanks to Michael Deckers.)
+
+    Pacific/Apia and Pacific/Pago_Pago switched from Antipodean to
+    American time in 1892, not 1879.  (Thanks to Michael Deckers.)
+
+    Adjust the 1867 transition in Alaska to better reflect the
+    historical record, by changing it to occur on 1867-10-18 at 15:30
+    Sitka time rather than at the start of 1867-10-17 local time.
+    Although strictly speaking this is accurate only for Sitka,
+    the rest of Alaska's blanks need to be filled in somehow.
+
+    Fix off-by-one errors in UT offsets for Adak and Nome before 1867.
+    (Thanks to Michael Deckers.)
+
+    Add 7 s to the UT offset in Asia/Yangon before 1920.
+
+  Changes to zone names
+
+    Remove Canada/East-Saskatchewan from the 'backward' file, as it
+    exceeded the 14-character limit and was an unused misnomer anyway.
+
+  Changes to build procedure
+
+    To support applications that prefer to read time zone data in text
+    form, two zic input files tzdata.zi and leapseconds are now
+    installed by default.  The commands 'zic tzdata.zi' and 'zic -L
+    leapseconds tzdata.zi' can reproduce the tzdata binary files
+    without and with leap seconds, respectively.  To prevent these two
+    new files from being installed, use 'make TZDATA_TEXT=', and to
+    suppress leap seconds from the tzdata text installation, use 'make
+    TZDATA_TEXT=tzdata.zi'.
+
+    'make BACKWARD=' now suppresses backward-compatibility names
+    like 'US/Pacific' that are defined in the 'backward' and
+    'pacificnew' files.
+
+    'make check' now works on systems that lack a UTF-8 locale,
+    or that lack the nsgmls program.  Set UTF8_LOCALE to configure
+    the name of a UTF-8 locale, if you have one.
+
+    Y2K runtime checks are no longer enabled by default.  Add
+    -DDEPRECATE_TWO_DIGIT_YEARS to CFLAGS to enable them, instead of
+    adding -DNO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
+    to disable them.  (New name suggested by Brian Inglis.)
+
+    The build procedure for zdump now works on AIX 7.1.
+    (Problem reported by Kees Dekker.)
+
+  Changes to code
+
+    zic and the reference runtime now reject multiple leap seconds
+    within 28 days of each other, or leap seconds before the Epoch.
+    As a result, support for double leap seconds, which was
+    obsolescent and undocumented, has been removed.  Double leap
+    seconds were an error in the C89 standard; they have never existed
+    in civil timekeeping.  (Thanks to Robert Elz and Bradley White for
+    noticing glitches in the code that uncovered this problem.)
+
+    zic now warns about use of the obsolescent and undocumented -y
+    option, and about use of the obsolescent TYPE field of Rule lines.
+
+    zic now allows unambiguous abbreviations like "Sa" and "Su" for
+    weekdays; formerly it rejected them due to a bug.  Conversely, zic
+    no longer considers non-prefixes to be abbreviations; for example,
+    it no longer accepts "lF" as an abbreviation for "lastFriday".
+    Also, zic warns about the undocumented usage with a "last-"
+    prefix, e.g., "last-Fri".
+
+    Similarly, zic now accepts the unambiguous abbreviation "L" for
+    "Link" in ordinary context and for "Leap" in leap-second context.
+    Conversely, zic no longer accepts non-prefixes such as "La" as
+    abbreviations for words like "Leap".
+
+    zic no longer accepts leap second lines in ordinary input, or
+    ordinary lines in leap second input.  Formerly, zic sometimes
+    warned about this undocumented usage and handled it incorrectly.
+
+    The new macro HAVE_TZNAME governs whether the tzname external
+    variable is exported, instead of USG_COMPAT.  USG_COMPAT now
+    governs only the external variables "timezone" and "daylight".
+    This change is needed because the three variables are not in the
+    same category: although POSIX requires tzname, it specifies the
+    other two variables as optional.  Also, USG_COMPAT is now 1 or 0:
+    if not defined, the code attempts to guess it from other macros.
+
+    localtime.c and difftime.c no longer require stdio.h, and .c files
+    other than zic.c no longer require sys/wait.h.
+
+    zdump.c no longer assumes snprintf.  (Reported by Jonathan Leffler.)
+
+    Calculation of time_t extrema works around a bug in GCC 4.8.4
+    (Reported by Stan Shebs and Joseph Myers.)
+
+    zic.c no longer mistranslates formats of line numbers in non-English
+    locales.  (Problem reported by Benno Schulenberg.)
+
+    Several minor changes have been made to the code to make it a
+    bit easier to port to MS-Windows and Solaris.  (Thanks to Kees
+    Dekker for reporting the problems.)
+
+  Changes to documentation and commentary
+
+    The two new files 'theory.html' and 'calendars' contain the
+    contents of the removed file 'Theory'.  The goal is to document
+    tzdb theory more accessibly.
+
+    The zic man page now documents abbreviation rules.
+
+    tz-link.htm now covers how to apply tzdata changes to clients.
+    (Thanks to Jorge Fábregas for the AIX link.)  It also mentions MySQL.
+
+    The leap-seconds.list URL has been updated to something that is
+    more reliable for tzdb.  (Thanks to Tim Parenti and Brian Inglis.)
+
 Release 2017b - 2017-03-17 07:30:38 -0700
 
   Briefly: Haiti has resumed DST.
@@ -15,6 +179,16 @@ Release 2017b - 2017-03-17 07:30:38 -0700
     Use "MMT" to abbreviate Liberia's time zone before 1972, as "-004430"
     is one byte over the POSIX limit.  (Problem reported by Derick Rethans.)
 
+  Changes to code
+
+    The reference localtime implementation now falls back on the
+    current US daylight-saving transition rules rather than the
+    1987-2006 rules.  This fallback occurs only when (1) the TZ
+    environment variable's value has a name like "AST4ADT" that asks
+    for daylight saving time but does not specify the rules, (2) there
+    is no file by that name, and (3) the TZDEFRULES file cannot be
+    loaded.  (Thanks to Tom Lane.)
+
 
 Release 2017a - 2017-02-28 00:05:36 -0800
 
@@ -1981,7 +2155,7 @@ Release 2013e - 2013-09-19 23:50:04 -0700
 
     The 'leapseconds' file is now generated automatically from a
     new file 'leap-seconds.list', which is a copy of
-    <ftp://time.nist.gov/pub/leap-seconds.list>.
+    <ftp://ftp.nist.gov/pub/time/leap-seconds.list>
     A new source file 'leapseconds.awk' implements this.
     The goal is simplification of the future maintenance of 'leapseconds'.
 
@@ -2187,7 +2361,7 @@ Release 2013a - 2013-02-27 09:20:35 -0800
 
   Many changes affect historical timestamps before 1940.
   These were deduced from: Milne J. Civil time. Geogr J. 1899
-  Feb;13(2):173-94 <http://www.jstor.org/stable/1774359>.
+  Feb;13(2):173-94 <https://www.jstor.org/stable/1774359>.
 
   Changes affecting the code:
 
diff --git a/contrib/tzdata/Theory b/contrib/tzdata/Theory
deleted file mode 100644
index 33e46069ba23..000000000000
--- a/contrib/tzdata/Theory
+++ /dev/null
@@ -1,870 +0,0 @@
-Theory and pragmatics of the tz code and data
-
-
------ Outline -----
-
-	Scope of the tz database
-	Names of time zone rules
-	Time zone abbreviations
-	Accuracy of the tz database
-	Time and date functions
-	Interface stability
-	Calendrical issues
-	Time and time zones on Mars
-
-
------ Scope of the tz database -----
-
-The tz database attempts to record the history and predicted future of
-all computer-based clocks that track civil time.  To represent this
-data, the world is partitioned into regions whose clocks all agree
-about time stamps that occur after the somewhat-arbitrary cutoff point
-of the POSIX Epoch (1970-01-01 00:00:00 UTC).  For each such region,
-the database records all known clock transitions, and labels the region
-with a notable location.  Although 1970 is a somewhat-arbitrary
-cutoff, there are significant challenges to moving the cutoff earlier
-even by a decade or two, due to the wide variety of local practices
-before computer timekeeping became prevalent.
-
-Clock transitions before 1970 are recorded for each such location,
-because most systems support time stamps before 1970 and could
-misbehave if data entries were omitted for pre-1970 transitions.
-However, the database is not designed for and does not suffice for
-applications requiring accurate handling of all past times everywhere,
-as it would take far too much effort and guesswork to record all
-details of pre-1970 civil timekeeping.
-
-As described below, reference source code for using the tz database is
-also available.  The tz code is upwards compatible with POSIX, an
-international standard for UNIX-like systems.  As of this writing, the
-current edition of POSIX is:
-
-  The Open Group Base Specifications Issue 7
-  IEEE Std 1003.1-2008, 2016 Edition
-  <http://pubs.opengroup.org/onlinepubs/9699919799/>
-
-
-
------ Names of time zone rules -----
-
-Each of the database's time zone rules has a unique name.
-Inexperienced users are not expected to select these names unaided.
-Distributors should provide documentation and/or a simple selection
-interface that explains the names; for one example, see the 'tzselect'
-program in the tz code.  The Unicode Common Locale Data Repository
-<http://cldr.unicode.org/> contains data that may be useful for other
-selection interfaces.
-
-The time zone rule naming conventions attempt to strike a balance
-among the following goals:
-
- * Uniquely identify every region where clocks have agreed since 1970.
-   This is essential for the intended use: static clocks keeping local
-   civil time.
-
- * Indicate to experts where that region is.
-
- * Be robust in the presence of political changes.  For example, names
-   of countries are ordinarily not used, to avoid incompatibilities
-   when countries change their name (e.g. Zaire->Congo) or when
-   locations change countries (e.g. Hong Kong from UK colony to
-   China).
-
- * Be portable to a wide variety of implementations.
-
- * Use a consistent naming conventions over the entire world.
-
-Names normally have the form AREA/LOCATION, where AREA is the name
-of a continent or ocean, and LOCATION is the name of a specific
-location within that region.  North and South America share the same
-area, 'America'.  Typical names are 'Africa/Cairo', 'America/New_York',
-and 'Pacific/Honolulu'.
-
-Here are the general rules used for choosing location names,
-in decreasing order of importance:
-
-	Use only valid POSIX file name components (i.e., the parts of
-		names other than '/').  Do not use the file name
-		components '.' and '..'.  Within a file name component,
-		use only ASCII letters, '.', '-' and '_'.  Do not use
-		digits, as that might create an ambiguity with POSIX
-		TZ strings.  A file name component must not exceed 14
-		characters or start with '-'.  E.g., prefer 'Brunei'
-		to 'Bandar_Seri_Begawan'.  Exceptions: see the discussion
-		of legacy names below.
-	A name must not be empty, or contain '//', or start or end with '/'.
-	Do not use names that differ only in case.  Although the reference
-		implementation is case-sensitive, some other implementations
-		are not, and they would mishandle names differing only in case.
-	If one name A is an initial prefix of another name AB (ignoring case),
-		then B must not start with '/', as a regular file cannot have
-		the same name as a directory in POSIX.  For example,
-		'America/New_York' precludes 'America/New_York/Bronx'.
-	Uninhabited regions like the North Pole and Bouvet Island
-		do not need locations, since local time is not defined there.
-	There should typically be at least one name for each ISO 3166-1
-		officially assigned two-letter code for an inhabited country
-		or territory.
-	If all the clocks in a region have agreed since 1970,
-		don't bother to include more than one location
-		even if subregions' clocks disagreed before 1970.
-		Otherwise these tables would become annoyingly large.
-	If a name is ambiguous, use a less ambiguous alternative;
-		e.g. many cities are named San José and Georgetown, so
-		prefer 'Costa_Rica' to 'San_Jose' and 'Guyana' to 'Georgetown'.
-	Keep locations compact.  Use cities or small islands, not countries
-		or regions, so that any future time zone changes do not split
-		locations into different time zones.  E.g. prefer 'Paris'
-		to 'France', since France has had multiple time zones.
-	Use mainstream English spelling, e.g. prefer 'Rome' to 'Roma', and
-		prefer 'Athens' to the Greek 'Αθήνα' or the Romanized 'Athína'.
-		The POSIX file name restrictions encourage this rule.
-	Use the most populous among locations in a zone,
-		e.g. prefer 'Shanghai' to 'Beijing'.  Among locations with
-		similar populations, pick the best-known location,
-		e.g. prefer 'Rome' to 'Milan'.
-	Use the singular form, e.g. prefer 'Canary' to 'Canaries'.
-	Omit common suffixes like '_Islands' and '_City', unless that
-		would lead to ambiguity.  E.g. prefer 'Cayman' to
-		'Cayman_Islands' and 'Guatemala' to 'Guatemala_City',
-		but prefer 'Mexico_City' to 'Mexico' because the country
-		of Mexico has several time zones.
-	Use '_' to represent a space.
-	Omit '.' from abbreviations in names, e.g. prefer 'St_Helena'
-		to 'St._Helena'.
-	Do not change established names if they only marginally
-		violate the above rules.  For example, don't change
-		the existing name 'Rome' to 'Milan' merely because
-		Milan's population has grown to be somewhat greater
-		than Rome's.
-	If a name is changed, put its old spelling in the 'backward' file.
-		This means old spellings will continue to work.
-
-The file 'zone1970.tab' lists geographical locations used to name time
-zone rules.  It is intended to be an exhaustive list of names for
-geographic regions as described above; this is a subset of the names
-in the data.  Although a 'zone1970.tab' location's longitude
-corresponds to its LMT offset with one hour for every 15 degrees east
-longitude, this relationship is not exact.
-
-Older versions of this package used a different naming scheme,
-and these older names are still supported.
-See the file 'backward' for most of these older names
-(e.g., 'US/Eastern' instead of 'America/New_York').
-The other old-fashioned names still supported are
-'WET', 'CET', 'MET', and 'EET' (see the file 'europe').
-
-Older versions of this package defined legacy names that are
-incompatible with the first rule of location names, but which are
-still supported.  These legacy names are mostly defined in the file
-'etcetera'.  Also, the file 'backward' defines the legacy names
-'GMT0', 'GMT-0', 'GMT+0' and 'Canada/East-Saskatchewan', and the file
-'northamerica' defines the legacy names 'EST5EDT', 'CST6CDT',
-'MST7MDT', and 'PST8PDT'.
-
-Excluding 'backward' should not affect the other data.  If
-'backward' is excluded, excluding 'etcetera' should not affect the
-remaining data.
-
-
------ Time zone abbreviations -----
-
-When this package is installed, it generates time zone abbreviations
-like 'EST' to be compatible with human tradition and POSIX.
-Here are the general rules used for choosing time zone abbreviations,
-in decreasing order of importance:
-
-	Use three or more characters that are ASCII alphanumerics or '+' or '-'.
-		Previous editions of this database also used characters like
-		' ' and '?', but these characters have a special meaning to
-		the shell and cause commands like
-			set `date`
-		to have unexpected effects.
-		Previous editions of this rule required upper-case letters,
-		but the Congressman who introduced Chamorro Standard Time
-		preferred "ChST", so lower-case letters are now allowed.
-		Also, POSIX from 2001 on relaxed the rule to allow '-', '+',
-		and alphanumeric characters from the portable character set
-		in the current locale.  In practice ASCII alphanumerics and
-		'+' and '-' are safe in all locales.
-
-		In other words, in the C locale the POSIX extended regular
-		expression [-+[:alnum:]]{3,} should match the abbreviation.
-		This guarantees that all abbreviations could have been
-		specified by a POSIX TZ string.
-
-	Use abbreviations that are in common use among English-speakers,
-		e.g. 'EST' for Eastern Standard Time in North America.
-		We assume that applications translate them to other languages
-		as part of the normal localization process; for example,
-		a French application might translate 'EST' to 'HNE'.
-
-	For zones whose times are taken from a city's longitude, use the
-		traditional xMT notation, e.g. 'PMT' for Paris Mean Time.
-		The only name like this in current use is 'GMT'.
-
-	Use 'LMT' for local mean time of locations before the introduction
-		of standard time; see "Scope of the tz database".
-
-	If there is no common English abbreviation, use numeric offsets like
-		-05 and +0830 that are generated by zic's %z notation.
-
-	Use current abbreviations for older timestamps to avoid confusion.
-		For example, in 1910 a common English abbreviation for UT +01
-		in central Europe was 'MEZ' (short for both "Middle European
-		Zone" and for "Mitteleuropäische Zeit" in German).  Nowadays
-		'CET' ("Central European Time") is more common in English, and
-		the database uses 'CET' even for circa-1910 timestamps as this
-		is less confusing for modern users and avoids the need for
-		determining when 'CET' supplanted 'MEZ' in common usage.
-
-	Use a consistent style in a zone's history.  For example, if a zone's
-		history tends to use numeric abbreviations and a particular
-		entry could go either way, use a numeric abbreviation.
-
-    [The remaining guidelines predate the introduction of %z.
-    They are problematic as they mean tz data entries invent
-    notation rather than record it.  These guidelines are now
-    deprecated and the plan is to gradually move to %z for
-    inhabited locations and to "-00" for uninhabited locations.]
-
-	If there is no common English abbreviation, abbreviate the English
-		translation of the usual phrase used by native speakers.
-		If this is not available or is a phrase mentioning the country
-		(e.g. "Cape Verde Time"), then:
-
-		When a country is identified with a single or principal zone,
-			append 'T' to the country's ISO	code, e.g. 'CVT' for
-			Cape Verde Time.  For summer time append 'ST';
-			for double summer time append 'DST'; etc.
-		Otherwise, take the first three letters of an English place
-			name identifying each zone and append 'T', 'ST', etc.
-			as before; e.g. 'CHAST' for CHAtham Summer Time.
-
-	Use UT (with time zone abbreviation '-00') for locations while
-		uninhabited.  The leading '-' is a flag that the time
-		zone is in some sense undefined; this notation is
-		derived from Internet RFC 3339.
-
-Application writers should note that these abbreviations are ambiguous
-in practice: e.g. 'CST' has a different meaning in China than
-it does in the United States.  In new applications, it's often better
-to use numeric UT offsets like '-0600' instead of time zone
-abbreviations like 'CST'; this avoids the ambiguity.
-
-
------ Accuracy of the tz database -----
-
-The tz database is not authoritative, and it surely has errors.
-Corrections are welcome and encouraged; see the file CONTRIBUTING.
-Users requiring authoritative data should consult national standards
-bodies and the references cited in the database's comments.
-
-Errors in the tz database arise from many sources:
-
- * The tz database predicts future time stamps, and current predictions
-   will be incorrect after future governments change the rules.
-   For example, if today someone schedules a meeting for 13:00 next
-   October 1, Casablanca time, and tomorrow Morocco changes its
-   daylight saving rules, software can mess up after the rule change
-   if it blithely relies on conversions made before the change.
-
- * The pre-1970 entries in this database cover only a tiny sliver of how
-   clocks actually behaved; the vast majority of the necessary
-   information was lost or never recorded.  Thousands more zones would
-   be needed if the tz database's scope were extended to cover even
-   just the known or guessed history of standard time; for example,
-   the current single entry for France would need to split into dozens
-   of entries, perhaps hundreds.  And in most of the world even this
-   approach would be misleading due to widespread disagreement or
-   indifference about what times should be observed.  In her 2015 book
-   "The Global Transformation of Time, 1870-1950", Vanessa Ogle writes
-   "Outside of Europe and North America there was no system of time
-   zones at all, often not even a stable landscape of mean times,
-   prior to the middle decades of the twentieth century".  See:
-   Timothy Shenk, Booked: A Global History of Time. Dissent 2015-12-17
-   https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanessa-ogle
-
- * Most of the pre-1970 data entries come from unreliable sources, often
-   astrology books that lack citations and whose compilers evidently
-   invented entries when the true facts were unknown, without
-   reporting which entries were known and which were invented.
-   These books often contradict each other or give implausible entries,
-   and on the rare occasions when they are checked they are
-   typically found to be incorrect.
-
- * For the UK the tz database relies on years of first-class work done by
-   Joseph Myers and others; see <http://www.polyomino.org.uk/british-time/>.
-   Other countries are not done nearly as well.
-
- * Sometimes, different people in the same city would maintain clocks
-   that differed significantly.  Railway time was used by railroad
-   companies (which did not always agree with each other),
-   church-clock time was used for birth certificates, etc.
-   Often this was merely common practice, but sometimes it was set by law.
-   For example, from 1891 to 1911 the UT offset in France was legally
-   0:09:21 outside train stations and 0:04:21 inside.
-
- * Although a named location in the tz database stands for the
-   containing region, its pre-1970 data entries are often accurate for
-   only a small subset of that region.  For example, Europe/London
-   stands for the United Kingdom, but its pre-1847 times are valid
-   only for locations that have London's exact meridian, and its 1847
-   transition to GMT is known to be valid only for the L&NW and the
-   Caledonian railways.
-
- * The tz database does not record the earliest time for which a zone's
-   data entries are thereafter valid for every location in the region.
-   For example, Europe/London is valid for all locations in its
-   region after GMT was made the standard time, but the date of
-   standardization (1880-08-02) is not in the tz database, other than
-   in commentary.  For many zones the earliest time of validity is
-   unknown.
-
- * The tz database does not record a region's boundaries, and in many
-   cases the boundaries are not known.  For example, the zone
-   America/Kentucky/Louisville represents a region around the city of
-   Louisville, the boundaries of which are unclear.
-
- * Changes that are modeled as instantaneous transitions in the tz
-   database were often spread out over hours, days, or even decades.
-
- * Even if the time is specified by law, locations sometimes
-   deliberately flout the law.
-
- * Early timekeeping practices, even assuming perfect clocks, were
-   often not specified to the accuracy that the tz database requires.
-
- * Sometimes historical timekeeping was specified more precisely
-   than what the tz database can handle.  For example, from 1909 to
-   1937 Netherlands clocks were legally UT +00:19:32.13, but the tz
-   database cannot represent the fractional second.
-
- * Even when all the timestamp transitions recorded by the tz database
-   are correct, the tz rules that generate them may not faithfully
-   reflect the historical rules.  For example, from 1922 until World
-   War II the UK moved clocks forward the day following the third
-   Saturday in April unless that was Easter, in which case it moved
-   clocks forward the previous Sunday.  Because the tz database has no
-   way to specify Easter, these exceptional years are entered as
-   separate tz Rule lines, even though the legal rules did not change.
-
- * The tz database models pre-standard time using the proleptic Gregorian
-   calendar and local mean time (LMT), but many people used other
-   calendars and other timescales.  For example, the Roman Empire used
-   the Julian calendar, and had 12 varying-length daytime hours with a
-   non-hour-based system at night.
-
- * Early clocks were less reliable, and data entries do not represent
-   clock error.
-
- * The tz database assumes Universal Time (UT) as an origin, even
-   though UT is not standardized for older time stamps.  In the tz
-   database commentary, UT denotes a family of time standards that
-   includes Coordinated Universal Time (UTC) along with other variants
-   such as UT1 and GMT, with days starting at midnight.  Although UT
-   equals UTC for modern time stamps, UTC was not defined until 1960,
-   so commentary uses the more-general abbreviation UT for time stamps
-   that might predate 1960.  Since UT, UT1, etc. disagree slightly,
-   and since pre-1972 UTC seconds varied in length, interpretation of
-   older time stamps can be problematic when subsecond accuracy is
-   needed.
-
- * Civil time was not based on atomic time before 1972, and we don't
-   know the history of earth's rotation accurately enough to map SI
-   seconds to historical solar time to more than about one-hour
-   accuracy.  See: Stephenson FR, Morrison LV, Hohenkerk CY.
-   Measurement of the Earth's rotation: 720 BC to AD 2015.
-   Proc Royal Soc A. 2016 Dec 7;472:20160404.
-   http://dx.doi.org/10.1098/rspa.2016.0404
-   Also see: Espenak F. Uncertainty in Delta T (ΔT).
-   http://eclipse.gsfc.nasa.gov/SEhelp/uncertainty2004.html
-
- * The relationship between POSIX time (that is, UTC but ignoring leap
-   seconds) and UTC is not agreed upon after 1972.  Although the POSIX
-   clock officially stops during an inserted leap second, at least one
-   proposed standard has it jumping back a second instead; and in
-   practice POSIX clocks more typically either progress glacially during
-   a leap second, or are slightly slowed while near a leap second.
-
- * The tz database does not represent how uncertain its information is.
-   Ideally it would contain information about when data entries are
-   incomplete or dicey.  Partial temporal knowledge is a field of
-   active research, though, and it's not clear how to apply it here.
-
-In short, many, perhaps most, of the tz database's pre-1970 and future
-time stamps are either wrong or misleading.  Any attempt to pass the
-tz database off as the definition of time should be unacceptable to
-anybody who cares about the facts.  In particular, the tz database's
-LMT offsets should not be considered meaningful, and should not prompt
-creation of zones merely because two locations differ in LMT or
-transitioned to standard time at different dates.
-
-
------ Time and date functions -----
-
-The tz code contains time and date functions that are upwards
-compatible with those of POSIX.
-
-POSIX has the following properties and limitations.
-
-*	In POSIX, time display in a process is controlled by the
-	environment variable TZ.  Unfortunately, the POSIX TZ string takes
-	a form that is hard to describe and is error-prone in practice.
-	Also, POSIX TZ strings can't deal with other (for example, Israeli)
-	daylight saving time rules, or situations where more than two
-	time zone abbreviations are used in an area.
-
-	The POSIX TZ string takes the following form:
-
-		stdoffset[dst[offset][,date[/time],date[/time]]]
-
-	where:
-
-	std and dst
-		are 3 or more characters specifying the standard
-		and daylight saving time (DST) zone names.
-		Starting with POSIX.1-2001, std and dst may also be
-		in a quoted form like "<UTC+10>"; this allows
-		"+" and "-" in the names.
-	offset
-		is of the form '[+-]hh:[mm[:ss]]' and specifies the
-		offset west of UT.  'hh' may be a single digit; 0<=hh<=24.
-		The default DST offset is one hour ahead of standard time.
-	date[/time],date[/time]
-		specifies the beginning and end of DST.  If this is absent,
-		the system supplies its own rules for DST, and these can
-		differ from year to year; typically US DST rules are used.
-	time
-		takes the form 'hh:[mm[:ss]]' and defaults to 02:00.
-		This is the same format as the offset, except that a
-		leading '+' or '-' is not allowed.
-	date
-		takes one of the following forms:
-		Jn (1<=n<=365)
-			origin-1 day number not counting February 29
-		n (0<=n<=365)
-			origin-0 day number counting February 29 if present
-		Mm.n.d (0[Sunday]<=d<=6[Saturday], 1<=n<=5, 1<=m<=12)
-			for the dth day of week n of month m of the year,
-			where week 1 is the first week in which day d appears,
-			and '5' stands for the last week in which day d appears
-			(which may be either the 4th or 5th week).
-			Typically, this is the only useful form;
-			the n and Jn forms are rarely used.
-
-	Here is an example POSIX TZ string, for US Pacific time using rules
-	appropriate from 1987 through 2006:
-
-		TZ='PST8PDT,M4.1.0/02:00,M10.5.0/02:00'
-
-	This POSIX TZ string is hard to remember, and mishandles time stamps
-	before 1987 and after 2006.  With this package you can use this
-	instead:
-
-		TZ='America/Los_Angeles'
-
-*	POSIX does not define the exact meaning of TZ values like "EST5EDT".
-	Typically the current US DST rules are used to interpret such values,
-	but this means that the US DST rules are compiled into each program
-	that does time conversion.  This means that when US time conversion
-	rules change (as in the United States in 1987), all programs that
-	do time conversion must be recompiled to ensure proper results.
-
-*	The TZ environment variable is process-global, which makes it hard
-	to write efficient, thread-safe applications that need access
-	to multiple time zones.
-
-*	In POSIX, there's no tamper-proof way for a process to learn the
-	system's best idea of local wall clock.  (This is important for
-	applications that an administrator wants used only at certain times -
-	without regard to whether the user has fiddled the "TZ" environment
-	variable.  While an administrator can "do everything in UTC" to get
-	around the problem, doing so is inconvenient and precludes handling
-	daylight saving time shifts - as might be required to limit phone
-	calls to off-peak hours.)
-
-*	POSIX provides no convenient and efficient way to determine the UT
-	offset and time zone abbreviation of arbitrary time stamps,
-	particularly for time zone settings that do not fit into the
-	POSIX model.
-
-*	POSIX requires that systems ignore leap seconds.
-
-*	The tz code attempts to support all the time_t implementations
-	allowed by POSIX.  The time_t type represents a nonnegative count of
-	seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds.
-	In practice, time_t is usually a signed 64- or 32-bit integer; 32-bit
-	signed time_t values stop working after 2038-01-19 03:14:07 UTC, so
-	new implementations these days typically use a signed 64-bit integer.
-	Unsigned 32-bit integers are used on one or two platforms,
-	and 36-bit and 40-bit integers are also used occasionally.
-	Although earlier POSIX versions allowed time_t to be a
-	floating-point type, this was not supported by any practical
-	systems, and POSIX.1-2013 and the tz code both require time_t
-	to be an integer type.
-
-These are the extensions that have been made to the POSIX functions:
-
-*	The "TZ" environment variable is used in generating the name of a file
-	from which time zone information is read (or is interpreted a la
-	POSIX); "TZ" is no longer constrained to be a three-letter time zone
-	name followed by a number of hours and an optional three-letter
-	daylight time zone name.  The daylight saving time rules to be used
-	for a particular time zone are encoded in the time zone file;
-	the format of the file allows U.S., Australian, and other rules to be
-	encoded, and allows for situations where more than two time zone
-	abbreviations are used.
-
-	It was recognized that allowing the "TZ" environment variable to
-	take on values such as "America/New_York" might cause "old" programs
-	(that expect "TZ" to have a certain form) to operate incorrectly;
-	consideration was given to using some other environment variable
-	(for example, "TIMEZONE") to hold the string used to generate the
-	time zone information file name.  In the end, however, it was decided
-	to continue using "TZ": it is widely used for time zone purposes;
-	separately maintaining both "TZ" and "TIMEZONE" seemed a nuisance;
-	and systems where "new" forms of "TZ" might cause problems can simply
-	use TZ values such as "EST5EDT" which can be used both by
-	"new" programs (a la POSIX) and "old" programs (as zone names and
-	offsets).
-
-*	The code supports platforms with a UT offset member in struct tm,
-	e.g., tm_gmtoff.
-
-*	The code supports platforms with a time zone abbreviation member in
-	struct tm, e.g., tm_zone.
-
-*	Since the "TZ" environment variable can now be used to control time
-	conversion, the "daylight" and "timezone" variables are no longer
-	needed.  (These variables are defined and set by "tzset"; however, their
-	values will not be used by "localtime.")
-
-*	Functions tzalloc, tzfree, localtime_rz, and mktime_z for
-	more-efficient thread-safe applications that need to use
-	multiple time zones.  The tzalloc and tzfree functions
-	allocate and free objects of type timezone_t, and localtime_rz
-	and mktime_z are like localtime_r and mktime with an extra
-	timezone_t argument.  The functions were inspired by NetBSD.
-
-*	A function "tzsetwall" has been added to arrange for the system's
-	best approximation to local wall clock time to be delivered by
-	subsequent calls to "localtime."  Source code for portable
-	applications that "must" run on local wall clock time should call
-	"tzsetwall();" if such code is moved to "old" systems that don't
-	provide tzsetwall, you won't be able to generate an executable program.
-	(These time zone functions also arrange for local wall clock time to be
-	used if tzset is called - directly or indirectly - and there's no "TZ"
-	environment variable; portable applications should not, however, rely
-	on this behavior since it's not the way SVR2 systems behave.)
-
-*	Negative time_t values are supported, on systems where time_t is signed.
-
-*	These functions can account for leap seconds, thanks to Bradley White.
-
-Points of interest to folks with other systems:
-
-*	Code compatible with this package is already part of many platforms,
-	including GNU/Linux, Android, the BSDs, Chromium OS, Cygwin, AIX, iOS,
-	BlackBery 10, macOS, Microsoft Windows, OpenVMS, and Solaris.
-	On such hosts, the primary use of this package
-	is to update obsolete time zone rule tables.
-	To do this, you may need to compile the time zone compiler
-	'zic' supplied with this package instead of using the system 'zic',
-	since the format of zic's input is occasionally extended,
-	and a platform may still be shipping an older zic.
-
-*	The UNIX Version 7 "timezone" function is not present in this package;
-	it's impossible to reliably map timezone's arguments (a "minutes west
-	of GMT" value and a "daylight saving time in effect" flag) to a
-	time zone abbreviation, and we refuse to guess.
-	Programs that in the past used the timezone function may now examine
-	tzname[localtime(&clock)->tm_isdst] to learn the correct time
-	zone abbreviation to use.  Alternatively, use
-	localtime(&clock)->tm_zone if this has been enabled.
-
-*	The 4.2BSD gettimeofday function is not used in this package.
-	This formerly let users obtain the current UTC offset and DST flag,
-	but this functionality was removed in later versions of BSD.
-
-*	In SVR2, time conversion fails for near-minimum or near-maximum
-	time_t values when doing conversions for places that don't use UT.
-	This package takes care to do these conversions correctly.
-	A comment in the source code tells how to get compatibly wrong
-	results.
-
-The functions that are conditionally compiled if STD_INSPIRED is defined
-should, at this point, be looked on primarily as food for thought.  They are
-not in any sense "standard compatible" - some are not, in fact, specified in
-*any* standard.  They do, however, represent responses of various authors to
-standardization proposals.
-
-Other time conversion proposals, in particular the one developed by folks at
-Hewlett Packard, offer a wider selection of functions that provide capabilities
-beyond those provided here.  The absence of such functions from this package
-is not meant to discourage the development, standardization, or use of such
-functions.  Rather, their absence reflects the decision to make this package
-contain valid extensions to POSIX, to ensure its broad acceptability.  If
-more powerful time conversion functions can be standardized, so much the
-better.
-
-
------ Interface stability -----
-
-The tz code and data supply the following interfaces:
-
- * A set of zone names as per "Names of time zone rules" above.
-
- * Library functions described in "Time and date functions" above.
-
- * The programs tzselect, zdump, and zic, documented in their man pages.
-
- * The format of zic input files, documented in the zic man page.
-
- * The format of zic output files, documented in the tzfile man page.
-
- * The format of zone table files, documented in zone1970.tab.
-
- * The format of the country code file, documented in iso3166.tab.
-
- * The version number of the code and data, as the first line of
-   the text file 'version' in each release.
-
-Interface changes in a release attempt to preserve compatibility with
-recent releases.  For example, tz data files typically do not rely on
-recently-added zic features, so that users can run older zic versions
-to process newer data files.  The tz-link.htm file describes how
-releases are tagged and distributed.
-
-Interfaces not listed above are less stable.  For example, users
-should not rely on particular UT offsets or abbreviations for time
-stamps, as data entries are often based on guesswork and these guesses
-may be corrected or improved.
-
-
------ Calendrical issues -----
-
-Calendrical issues are a bit out of scope for a time zone database,
-but they indicate the sort of problems that we would run into if we
-extended the time zone database further into the past.  An excellent
-resource in this area is Nachum Dershowitz and Edward M. Reingold,
-Calendrical Calculations: Third Edition, Cambridge University Press (2008)
-<http://emr.cs.iit.edu/home/reingold/calendar-book/third-edition/>.
-Other information and sources are given below.  They sometimes disagree.
-
-
-France
-
-Gregorian calendar adopted 1582-12-20.
-French Revolutionary calendar used 1793-11-24 through 1805-12-31,
-and (in Paris only) 1871-05-06 through 1871-05-23.
-
-
-Russia
-
-From Chris Carrier (1996-12-02):
-On 1929-10-01 the Soviet Union instituted an "Eternal Calendar"
-with 30-day months plus 5 holidays, with a 5-day week.
-On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the
-Gregorian calendar while retaining the 6-day week; on 1940-06-27 it
-reverted to the 7-day week.  With the 6-day week the usual days
-off were the 6th, 12th, 18th, 24th and 30th of the month.
-(Source: Evitiar Zerubavel, _The Seven Day Circle_)
-
-
-Mark Brader reported a similar story in "The Book of Calendars", edited
-by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377.  But:
-
-From: Petteri Sulonen (via Usenet)
-Date: 14 Jan 1999 00:00:00 GMT
-...
-
-If your source is correct, how come documents between 1929 and 1940 were
-still dated using the conventional, Gregorian calendar?
-
-I can post a scan of a document dated December 1, 1934, signed by
-Yenukidze, the secretary, on behalf of Kalinin, the President of the
-Executive Committee of the Supreme Soviet, if you like.
-
-
-
-Sweden (and Finland)
-
-From: Mark Brader
-Subject: Re: Gregorian reform - a part of locale?
-<news:1996Jul6.012937.29190@sq.com>
-Date: 1996-07-06
-
-In 1700, Denmark made the transition from Julian to Gregorian.  Sweden
-decided to *start* a transition in 1700 as well, but rather than have one of
-those unsightly calendar gaps :-), they simply decreed that the next leap
-year after 1696 would be in 1744 - putting the whole country on a calendar
-different from both Julian and Gregorian for a period of 40 years.
-
-However, in 1704 something went wrong and the plan was not carried through;
-they did, after all, have a leap year that year.  And one in 1708.  In 1712
-they gave it up and went back to Julian, putting 30 days in February that
-year!...
-
-Then in 1753, Sweden made the transition to Gregorian in the usual manner,
-getting there only 13 years behind the original schedule.
-
-(A previous posting of this story was challenged, and Swedish readers
-produced the following references to support it: "Tideräkning och historia"
-by Natanael Beckman (1924) and "Tid, en bok om tideräkning och
-kalenderväsen" by Lars-Olof Lodén (1968).
-
-
-Grotefend's data
-
-From: "Michael Palmer" [with one obvious typo fixed]
-Subject: Re: Gregorian Calendar (was Re: Another FHC related question
-Newsgroups: soc.genealogy.german
-Date: Tue, 9 Feb 1999 02:32:48 -800
-...
-
-The following is a(n incomplete) listing, arranged chronologically, of
-European states, with the date they converted from the Julian to the
-Gregorian calendar:
-
-04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman
-                 Catholics and Danzig only)
-09/20 Dec 1582 - France, Lorraine
-
-21 Dec 1582/
-   01 Jan 1583 - Holland, Brabant, Flanders, Hennegau
-10/21 Feb 1583 - bishopric of Liege (Lüttich)
-13/24 Feb 1583 - bishopric of Augsburg
-04/15 Oct 1583 - electorate of Trier
-05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg,
-                 Salzburg, Brixen
-13/24 Oct 1583 - Austrian Oberelsaß and Breisgau
-20/31 Oct 1583 - bishopric of Basel
-02/13 Nov 1583 - duchy of Jülich-Berg
-02/13 Nov 1583 - electorate and city of Köln
-04/15 Nov 1583 - bishopric of Würzburg
-11/22 Nov 1583 - electorate of Mainz
-16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden
-17/28 Nov 1583 - bishopric of Münster and duchy of Cleve
-14/25 Dec 1583 - Steiermark
-
-06/17 Jan 1584 - Austria and Bohemia
-11/22 Jan 1584 - Lucerne, Uri, Schwyz, Zug, Freiburg, Solothurn
-12/23 Jan 1584 - Silesia and the Lausitz
-22 Jan/
-   02 Feb 1584 - Hungary (legally on 21 Oct 1587)
-      Jun 1584 - Unterwalden
-01/12 Jul 1584 - duchy of Westfalen
-
-16/27 Jun 1585 - bishopric of Paderborn
-
-14/25 Dec 1590 - Transylvania
-
-22 Aug/
-   02 Sep 1612 - duchy of Prussia
-
-13/24 Dec 1614 - Pfalz-Neuburg
-
-          1617 - duchy of Kurland (reverted to the Julian calendar in
-                 1796)
-
-          1624 - bishopric of Osnabrück
-
-          1630 - bishopric of Minden
-
-15/26 Mar 1631 - bishopric of Hildesheim
-
-          1655 - Kanton Wallis
-
-05/16 Feb 1682 - city of Strassburg
-
-18 Feb/
-   01 Mar 1700 - Protestant Germany (including Swedish possessions in
-                 Germany), Denmark, Norway
-30 Jun/
-   12 Jul 1700 - Gelderland, Zutphen
-10 Nov/
-   12 Dec 1700 - Utrecht, Overijssel
-
-31 Dec 1700/
-   12 Jan 1701 - Friesland, Groningen, Zürich, Bern, Basel, Geneva,
-                 Turgau, and Schaffhausen
-
-          1724 - Glarus, Appenzell, and the city of St. Gallen
-
-01 Jan 1750    - Pisa and Florence
-
-02/14 Sep 1752 - Great Britain
-
-17 Feb/
-   01 Mar 1753 - Sweden
-
-1760-1812      - Graubünden
-
-The Russian empire (including Finland and the Baltic states) did not
-convert to the Gregorian calendar until the Soviet revolution of 1917.
-
-Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen
-Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend
-(Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28.
-
-
------ Time and time zones on Mars -----
-
-Some people's work schedules use Mars time.  Jet Propulsion Laboratory
-(JPL) coordinators have kept Mars time on and off at least since 1997
-for the Mars Pathfinder mission.  Some of their family members have
-also adapted to Mars time.  Dozens of special Mars watches were built
-for JPL workers who kept Mars time during the Mars Exploration
-Rovers mission (2004).  These timepieces look like normal Seikos and
-Citizens but use Mars seconds rather than terrestrial seconds.
-
-A Mars solar day is called a "sol" and has a mean period equal to
-about 24 hours 39 minutes 35.244 seconds in terrestrial time.  It is
-divided into a conventional 24-hour clock, so each Mars second equals
-about 1.02749125 terrestrial seconds.
-
-The prime meridian of Mars goes through the center of the crater
-Airy-0, named in honor of the British astronomer who built the
-Greenwich telescope that defines Earth's prime meridian.  Mean solar
-time on the Mars prime meridian is called Mars Coordinated Time (MTC).
-
-Each landed mission on Mars has adopted a different reference for
-solar time keeping, so there is no real standard for Mars time zones.
-For example, the Mars Exploration Rover project (2004) defined two
-time zones "Local Solar Time A" and "Local Solar Time B" for its two
-missions, each zone designed so that its time equals local true solar
-time at approximately the middle of the nominal mission.  Such a "time
-zone" is not particularly suited for any application other than the
-mission itself.
-
-Many calendars have been proposed for Mars, but none have achieved
-wide acceptance.  Astronomers often use Mars Sol Date (MSD) which is a
-sequential count of Mars solar days elapsed since about 1873-12-29
-12:00 GMT.
-
-The tz database does not currently support Mars time, but it is
-documented here in the hopes that support will be added eventually.
-
-Sources:
-
-Michael Allison and Robert Schmunk,
-"Technical Notes on Mars Solar Time as Adopted by the Mars24 Sunclock"
-<http://www.giss.nasa.gov/tools/mars24/help/notes.html> (2012-08-08).
-
-Jia-Rui Chong, "Workdays Fit for a Martian", Los Angeles Times
-<http://articles.latimes.com/2004/jan/14/science/sci-marstime14>
-(2004-01-14), pp A1, A20-A21.
-
-Tom Chmielewski, "Jet Lag Is Worse on Mars", The Atlantic (2015-02-26)
-<http://www.theatlantic.com/technology/archive/2015/02/jet-lag-is-worse-on-mars/386033/>
-
------
-
-This file is in the public domain, so clarified as of 2009-05-17 by
-Arthur David Olson.
-
------
-Local Variables:
-coding: utf-8
-End:
diff --git a/contrib/tzdata/africa b/contrib/tzdata/africa
index dcc20b9b1c33..3a60bc27d02c 100644
--- a/contrib/tzdata/africa
+++ b/contrib/tzdata/africa
@@ -26,7 +26,7 @@
 #
 # For data circa 1899, a common source is:
 # Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94.
-# http://www.jstor.org/stable/1774359
+# https://www.jstor.org/stable/1774359
 #
 # A reliable and entertaining source about time zones is
 # Derek Howse, Greenwich time and longitude, Philip Wilson Publishers (1997).
@@ -218,7 +218,7 @@ Rule	Egypt	2006	only	-	Sep	21	24:00	0	-
 # saving time in Egypt will end in the night of 2007-09-06 to 2007-09-07.
 # From Jesper Nørgaard Welen (2007-08-15): [The following agree:]
 # http://www.nentjes.info/Bill/bill5.htm
-# http://www.timeanddate.com/worldclock/city.html?n=53
+# https://www.timeanddate.com/worldclock/city.html?n=53
 # From Steffen Thorsen (2007-09-04): The official information...:
 # http://www.sis.gov.eg/En/EgyptOnline/Miscellaneous/000002/0207000000000000001580.htm
 Rule	Egypt	2007	only	-	Sep	Thu>=1	24:00	0	-
@@ -256,8 +256,8 @@ Rule	Egypt	2007	only	-	Sep	Thu>=1	24:00	0	-
 # timeanddate[2] and another site I've found[3] also support that.
 #
 # [1] https://bugzilla.redhat.com/show_bug.cgi?id=492263
-# [2] http://www.timeanddate.com/worldclock/clockchange.html?n=53
-# [3] http://wwp.greenwichmeantime.com/time-zone/africa/egypt/
+# [2] https://www.timeanddate.com/worldclock/clockchange.html?n=53
+# [3] https://wwp.greenwichmeantime.com/time-zone/africa/egypt/
 
 # From Arthur David Olson (2009-04-20):
 # In 2009 (and for the next several years), Ramadan ends before the fourth
@@ -267,10 +267,10 @@ Rule	Egypt	2007	only	-	Sep	Thu>=1	24:00	0	-
 # From Steffen Thorsen (2009-08-11):
 # We have been able to confirm the August change with the Egyptian Cabinet
 # Information and Decision Support Center:
-# http://www.timeanddate.com/news/time/egypt-dst-ends-2009.html
+# https://www.timeanddate.com/news/time/egypt-dst-ends-2009.html
 #
 # The Middle East News Agency
-# http://www.mena.org.eg/index.aspx
+# https://www.mena.org.eg/index.aspx
 # also reports "Egypt starts winter time on August 21"
 # today in article numbered "71, 11/08/2009 12:25 GMT."
 # Only the title above is available without a subscription to their service,
@@ -320,7 +320,7 @@ Rule	Egypt	2007	only	-	Sep	Thu>=1	24:00	0	-
 # Thursday of April....  Clocks will still be turned back for Ramadan, but
 # dates not yet announced....
 # http://almogaz.com/news/weird-news/2015/04/05/1947105 ...
-# http://www.timeanddate.com/news/time/egypt-starts-dst-2015.html
+# https://www.timeanddate.com/news/time/egypt-starts-dst-2015.html
 
 # From Ahmed Nazmy (2015-04-20):
 # Egypt's ministers cabinet just announced ... that it will cancel DST at
@@ -447,11 +447,11 @@ Zone	Africa/Monrovia	-0:43:08 -	LMT	1882
 
 # From Even Scharning (2012-11-10):
 # Libya set their time one hour back at 02:00 on Saturday November 10.
-# http://www.libyaherald.com/2012/11/04/clocks-to-go-back-an-hour-on-saturday/
+# https://www.libyaherald.com/2012/11/04/clocks-to-go-back-an-hour-on-saturday/
 # Here is an official source [in Arabic]: http://ls.ly/fb6Yc
 #
 # Steffen Thorsen forwarded a translation (2012-11-10) in
-# http://mm.icann.org/pipermail/tz/2012-November/018451.html
+# https://mm.icann.org/pipermail/tz/2012-November/018451.html
 #
 # From Tim Parenti (2012-11-11):
 # Treat the 2012-11-10 change as a zone change from UTC+2 to UTC+1.
@@ -462,7 +462,7 @@ Zone	Africa/Monrovia	-0:43:08 -	LMT	1882
 # From Even Scharning (2013-10-25):
 # The scheduled end of DST in Libya on Friday, October 25, 2013 was
 # cancelled yesterday....
-# http://www.libyaherald.com/2013/10/24/correction-no-time-change-tomorrow/
+# https://www.libyaherald.com/2013/10/24/correction-no-time-change-tomorrow/
 #
 # From Paul Eggert (2013-10-25):
 # For now, assume they're reverting to the pre-2012 rules of permanent UT +02.
@@ -515,7 +515,7 @@ Zone	Africa/Tripoli	0:52:44 -	LMT	1920
 # basis....
 # It seems that Mauritius observed daylight saving time from 1982-10-10 to
 # 1983-03-20 as well, but that was not successful....
-# http://www.timeanddate.com/news/time/mauritius-daylight-saving-time.html
+# https://www.timeanddate.com/news/time/mauritius-daylight-saving-time.html
 
 # From Alex Krivenyshev (2008-06-25):
 # http://economicdevelopment.gov.mu/portal/site/Mainhomepage/menuitem.a42b24128104d9845dabddd154508a0c/?content_id=0a7cee8b5d69a110VgnVCM1000000a04a8c0RCRD
@@ -583,7 +583,7 @@ Zone	Africa/Tripoli	0:52:44 -	LMT	1920
 # http://lexpress.mu/Story/3398~Beebeejaun---Les-objectifs-d-%C3%A9conomie-d-%C3%A9nergie-de-l-heure-d-%C3%A9t%C3%A9-ont-%C3%A9t%C3%A9-atteints-
 #
 # Our wrap-up:
-# http://www.timeanddate.com/news/time/mauritius-dst-will-not-repeat.html
+# https://www.timeanddate.com/news/time/mauritius-dst-will-not-repeat.html
 
 # From Arthur David Olson (2009-07-11):
 # The "mauritius-dst-will-not-repeat" wrapup includes this:
@@ -615,7 +615,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # be one hour ahead of GMT between 1 June and 27 September, according to
 # Communication Minister and Government Spokesman, Khalid Naciri...."
 #
-# http://www.worldtimezone.net/dst_news/dst_news_morocco01.html
+# http://www.worldtimezone.com/dst_news/dst_news_morocco01.html
 # http://en.afrik.com/news11892.html
 
 # From Alex Krivenyshev (2008-05-09):
@@ -628,7 +628,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 
 # From Patrice Scattolin (2008-05-09):
 # According to this article:
-# http://www.avmaroc.com/actualite/heure-dete-comment-a127896.html
+# https://www.avmaroc.com/actualite/heure-dete-comment-a127896.html
 # (and republished here: <http://www.actu.ma/heure-dete-comment_i127896_0.html>)
 # the changes occur at midnight:
 #
@@ -650,7 +650,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # posted in English).
 #
 # The following Google query will generate many relevant hits:
-# http://www.google.com/search?hl=en&q=Conseil+de+gouvernement+maroc+heure+avance&btnG=Search
+# https://www.google.com/search?hl=en&q=Conseil+de+gouvernement+maroc+heure+avance&btnG=Search
 
 # From Steffen Thorsen (2008-08-27):
 # Morocco will change the clocks back on the midnight between August 31
@@ -661,7 +661,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # http://www.menara.ma/fr/Actualites/Maroc/Societe/ci.retour_a_l_heure_gmt_a_partir_du_dimanche_31_aout_a_minuit_officiel_.default
 #
 # We have some further details posted here:
-# http://www.timeanddate.com/news/time/morocco-ends-dst-early-2008.html
+# https://www.timeanddate.com/news/time/morocco-ends-dst-early-2008.html
 
 # From Steffen Thorsen (2009-03-17):
 # Morocco will observe DST from 2009-06-01 00:00 to 2009-08-21 00:00 according
@@ -671,7 +671,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # (French)
 #
 # Our summary:
-# http://www.timeanddate.com/news/time/morocco-starts-dst-2009.html
+# https://www.timeanddate.com/news/time/morocco-starts-dst-2009.html
 
 # From Alexander Krivenyshev (2009-03-17):
 # Here is a link to official document from Royaume du Maroc Premier Ministre,
@@ -694,7 +694,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # http://www.lavieeco.com/actualites/4099-le-maroc-passera-a-l-heure-d-ete-gmt1-le-2-mai.html
 # (French)
 # Our page:
-# http://www.timeanddate.com/news/time/morocco-starts-dst-2010.html
+# https://www.timeanddate.com/news/time/morocco-starts-dst-2010.html
 
 # From Dan Abitol (2011-03-30):
 # ...Rules for Africa/Casablanca are the following (24h format)
@@ -711,7 +711,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # They said that the decision was already taken.
 #
 # More articles in the press
-# http://www.yabiladi.com/articles/details/5058/secret-l-heure-d-ete-maroc-leve.html
+# https://www.yabiladi.com/articles/details/5058/secret-l-heure-d-ete-maroc-leve.html
 # http://www.lematin.ma/Actualite/Express/Article.asp?id=148923
 # http://www.lavieeco.com/actualite/Le-Maroc-passe-sur-GMT%2B1-a-partir-de-dim
 
@@ -803,7 +803,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # 1433 (18 April 2012) and the decision of the Head of Government of
 # 16 N. 3-29-15 Chaaban 1435 (4 June 2015).
 # Source (french):
-# http://lnt.ma/le-maroc-reculera-dune-heure-le-dimanche-14-juin/
+# https://lnt.ma/le-maroc-reculera-dune-heure-le-dimanche-14-juin/
 #
 # From Milamber (2015-06-09):
 # http://www.mmsp.gov.ma/fr/actualites.aspx?id=863
@@ -812,7 +812,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # [The gov.ma announcement] would (probably) make the switch on 2015-07-19 go
 # from 03:00 to 04:00 rather than from 02:00 to 03:00, as in the patch....
 # I think the patch is correct and the quoted text is wrong; the text in
-# <http://lnt.ma/le-maroc-reculera-dune-heure-le-dimanche-14-juin/> agrees
+# <https://lnt.ma/le-maroc-reculera-dune-heure-le-dimanche-14-juin/> agrees
 # with the patch.
 
 # From Paul Eggert (2015-06-08):
@@ -937,9 +937,17 @@ Link Africa/Maputo Africa/Kigali	# Rwanda
 Link Africa/Maputo Africa/Lubumbashi	# E Dem. Rep. of Congo
 Link Africa/Maputo Africa/Lusaka	# Zambia
 
+
 # Namibia
-# The 1994-04-03 transition is from Shanks & Pottenger.
-# Shanks & Pottenger report no DST after 1998-04; go with IATA.
+
+# From Arthur David Olson (2017-08-09):
+# The text of the "Namibia Time Act, 1994" is available online at
+# www.lac.org.na/laws/1994/811.pdf
+# and includes this nugget:
+# Notwithstanding the provisions of subsection (2) of section 1, the
+# first winter period after the commencement of this Act shall
+# commence at OOhOO on Monday 21 March 1994 and shall end at 02h00 on
+# Sunday 4 September 1994.
 
 # From Petronella Sibeene (2007-03-30):
 # http://allafrica.com/stories/200703300178.html
@@ -955,19 +963,30 @@ Link Africa/Maputo Africa/Lusaka	# Zambia
 # observes Botswana time, we have no details about historical practice.
 # In the meantime people there can use Africa/Gaborone.
 # See: Immanuel S. The Namibian. 2017-02-23.
-# http://www.namibian.com.na/51480/read/Time-change-divides-lawmakers
+# https://www.namibian.com.na/51480/read/Time-change-divides-lawmakers
+
+# From Steffen Thorsen (2017-08-09):
+# Namibia is going to change their time zone to what is now their DST:
+# https://www.newera.com.na/2017/02/23/namibias-winter-time-might-be-repealed/
+# This video is from the government decision:
+# https://www.nbc.na/news/na-passes-namibia-time-bill-repealing-1994-namibia-time-act.8665
+# We have made the assumption so far that they will change their time zone at
+# the same time they would normally start DST, the first Sunday in September:
+# https://www.timeanddate.com/news/time/namibia-new-time-zone.html
 
 # RULE	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-Rule	Namibia	1994	max	-	Sep	Sun>=1	2:00	1:00	S
-Rule	Namibia	1995	max	-	Apr	Sun>=1	2:00	0	-
+Rule	Namibia	1994	only	-	Mar	21	0:00	0	-
+Rule	Namibia	1994	2016	-	Sep	Sun>=1	2:00	1:00	S
+Rule	Namibia	1995	2017	-	Apr	Sun>=1	2:00	0	-
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Africa/Windhoek	1:08:24 -	LMT	1892 Feb 8
 			1:30	-	+0130	1903 Mar
 			2:00	-	SAST	1942 Sep 20  2:00
 			2:00	1:00	SAST	1943 Mar 21  2:00
 			2:00	-	SAST	1990 Mar 21 # independence
-			2:00	-	CAT	1994 Apr  3
-			1:00	Namibia	WA%sT
+			2:00	-	CAT	1994 Mar 21  0:00
+			1:00	Namibia	WA%sT	2017 Sep  3  2:00
+			2:00	-	CAT
 
 # Niger
 # See Africa/Lagos.
@@ -1054,14 +1073,24 @@ Link Africa/Johannesburg Africa/Mbabane    # Swaziland
 # no information
 
 # Sudan
-#
+
 # From <http://www.sunanews.net/sn13jane.html>
 # Sudan News Agency (2000-01-13),
 # also reported by Michaël De Beukelaer-Dossche via Steffen Thorsen:
 # Clocks will be moved ahead for 60 minutes all over the Sudan as of noon
 # Saturday....  This was announced Thursday by Caretaker State Minister for
 # Manpower Abdul-Rahman Nur-Eddin.
+
+# From Ahmed Atyya, National Telecommunications Corp. (NTC), Sudan (2017-10-17):
+# ... the Republic of Sudan is going to change the time zone from (GMT+3:00)
+# to (GMT+ 2:00) starting from Wednesday 1 November 2017.
 #
+# From Paul Eggert (2017-10-18):
+# A scanned copy (in Arabic) of Cabinet Resolution No. 352 for the
+# year 2017 can be found as an attachment in email today from Yahia
+# Abdalla of NTC, archived at:
+# https://mm.icann.org/pipermail/tz/2017-October/025333.html
+
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	Sudan	1970	only	-	May	 1	0:00	1:00	S
 Rule	Sudan	1970	1985	-	Oct	15	0:00	0	-
@@ -1070,10 +1099,14 @@ Rule	Sudan	1972	1985	-	Apr	lastSun	0:00	1:00	S
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Africa/Khartoum	2:10:08 -	LMT	1931
 			2:00	Sudan	CA%sT	2000 Jan 15 12:00
-			3:00	-	EAT
+			3:00	-	EAT	2017 Nov  1
+			2:00	-	CAT
 
 # South Sudan
-Link Africa/Khartoum Africa/Juba
+# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
+Zone	Africa/Juba	2:06:28 -	LMT	1931
+			2:00	Sudan	CA%sT	2000 Jan 15 12:00
+			3:00	-	EAT
 
 # Swaziland
 # See Africa/Johannesburg.
@@ -1111,11 +1144,11 @@ Link Africa/Khartoum Africa/Juba
 # According to several news sources, Tunisia will not observe DST this year.
 # (Arabic)
 # http://www.elbashayer.com/?page=viewn&nid=42546
-# http://www.babnet.net/kiwidetail-15295.asp
+# https://www.babnet.net/kiwidetail-15295.asp
 #
 # We have also confirmed this with the US embassy in Tunisia.
 # We have a wrap-up about this on the following page:
-# http://www.timeanddate.com/news/time/tunisia-cancels-dst-2009.html
+# https://www.timeanddate.com/news/time/tunisia-cancels-dst-2009.html
 
 # From Alexander Krivenyshev (2009-03-17):
 # Here is a link to Tunis Afrique Presse News Agency
diff --git a/contrib/tzdata/antarctica b/contrib/tzdata/antarctica
index 3332d6684252..d9c132a30f45 100644
--- a/contrib/tzdata/antarctica
+++ b/contrib/tzdata/antarctica
@@ -26,7 +26,7 @@
 # Heard Island, McDonald Islands (uninhabited)
 #	previously sealers and scientific personnel wintered
 #	Margaret Turner reports
-#	http://web.archive.org/web/20021204222245/http://www.dstc.qut.edu.au/DST/marg/daylight.html
+#	https://web.archive.org/web/20021204222245/http://www.dstc.qut.edu.au/DST/marg/daylight.html
 #	(1999-09-30) that they're UT +05, with no DST;
 #	presumably this is when they have visitors.
 #
@@ -47,7 +47,7 @@
 # http://www.aad.gov.au/default.asp?casid=37079
 #
 # We have more background information here:
-# http://www.timeanddate.com/news/time/antarctica-new-times.html
+# https://www.timeanddate.com/news/time/antarctica-new-times.html
 
 # From Steffen Thorsen (2010-03-10):
 # We got these changes from the Australian Antarctic Division: ...
@@ -62,7 +62,7 @@
 # - Mawson station stays on UTC+5.
 #
 # Background:
-# http://www.timeanddate.com/news/time/antartica-time-changes-2010.html
+# https://www.timeanddate.com/news/time/antartica-time-changes-2010.html
 
 # From Steffen Thorsen (2016-10-28):
 # Australian Antarctica Division informed us that Casey changed time
@@ -145,7 +145,7 @@ Zone Indian/Kerguelen	0	-	-00	1950 # Port-aux-Français
 #
 # year-round base in the main continent
 # Dumont d'Urville, Île des Pétrels, -6640+14001, since 1956-11
-# <http://en.wikipedia.org/wiki/Dumont_d'Urville_Station> (2005-12-05)
+# <https://en.wikipedia.org/wiki/Dumont_d'Urville_Station> (2005-12-05)
 #
 # Another base at Port-Martin, 50km east, began operation in 1947.
 # It was destroyed by fire on 1952-01-14.
diff --git a/contrib/tzdata/asia b/contrib/tzdata/asia
index 35774c6d7edd..ac39af351ecd 100644
--- a/contrib/tzdata/asia
+++ b/contrib/tzdata/asia
@@ -26,7 +26,7 @@
 #
 # For data circa 1899, a common source is:
 # Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94.
-# http://www.jstor.org/stable/1774359
+# https://www.jstor.org/stable/1774359
 #
 # For Russian data circa 1919, a source is:
 # Byalokoz EL. New Counting of Time in Russia since July 1, 1919.
@@ -75,8 +75,8 @@ Rule E-EurAsia	1996	max	-	Oct	lastSun	 0:00	0	-
 Rule RussiaAsia	1981	1984	-	Apr	1	 0:00	1:00	S
 Rule RussiaAsia	1981	1983	-	Oct	1	 0:00	0	-
 Rule RussiaAsia	1984	1995	-	Sep	lastSun	 2:00s	0	-
-Rule RussiaAsia	1985	2011	-	Mar	lastSun	 2:00s	1:00	S
-Rule RussiaAsia	1996	2011	-	Oct	lastSun	 2:00s	0	-
+Rule RussiaAsia	1985	2010	-	Mar	lastSun	 2:00s	1:00	S
+Rule RussiaAsia	1996	2010	-	Oct	lastSun	 2:00s	0	-
 
 # Afghanistan
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
@@ -109,13 +109,17 @@ Zone	Asia/Kabul	4:36:48 -	LMT	1890
 # or
 # (brief)
 # http://www.worldtimezone.com/dst_news/dst_news_armenia03.html
+# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule Armenia	2011	only	-	Mar	lastSun	 2:00s	1:00	S
+Rule Armenia	2011	only	-	Oct	lastSun	 2:00s	0	-
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Asia/Yerevan	2:58:00 -	LMT	1924 May  2
 			3:00	-	+03	1957 Mar
 			4:00 RussiaAsia +04/+05	1991 Mar 31  2:00s
 			3:00 RussiaAsia	+03/+04	1995 Sep 24  2:00s
 			4:00	-	+04	1997
-			4:00 RussiaAsia	+04/+05
+			4:00 RussiaAsia	+04/+05	2011
+			4:00	Armenia	+04/+05
 
 # Azerbaijan
 
@@ -127,7 +131,7 @@ Zone	Asia/Yerevan	2:58:00 -	LMT	1924 May  2
 # From Steffen Thorsen (2016-03-17):
 # ... the Azerbaijani Cabinet of Ministers has cancelled switching to
 # daylight saving time....
-# http://www.azernews.az/azerbaijan/94137.html
+# https://www.azernews.az/azerbaijan/94137.html
 # http://vestnikkavkaza.net/news/Azerbaijani-Cabinet-of-Ministers-cancels-daylight-saving-time.html
 # http://en.apa.az/xeber_azerbaijan_abolishes_daylight_savings_ti_240862.html
 
@@ -168,11 +172,11 @@ Zone	Asia/Baku	3:19:24 -	LMT	1924 May  2
 # the 19th and 20th, and they have not set the end date yet.
 #
 # Some sources:
-# http://in.reuters.com/article/southAsiaNews/idINIndia-40017620090601
+# https://in.reuters.com/article/southAsiaNews/idINIndia-40017620090601
 # http://bdnews24.com/details.php?id=85889&cid=2
 #
 # Our wrap-up:
-# http://www.timeanddate.com/news/time/bangladesh-daylight-saving-2009.html
+# https://www.timeanddate.com/news/time/bangladesh-daylight-saving-2009.html
 
 # From A. N. M. Kamrus Saadat (2009-06-15):
 # Finally we've got the official mail regarding DST start time where DST start
@@ -258,9 +262,15 @@ Zone	Asia/Brunei	7:39:40 -	LMT	1926 Mar # Bandar Seri Begawan
 
 # Milne says 6:24:40 was the meridian of the time ball observatory at Rangoon.
 
+# From Paul Eggert (2017-04-20):
+# Page 27 of Reed & Low (cited for Asia/Kolkata) says "Rangoon local time is
+# used upon the railways and telegraphs of Burma, and is 6h. 24m. 47s. ahead
+# of Greenwich."  This refers to the period before Burma's transition to +0630,
+# a transition for which Shanks is the only source.
+
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Asia/Yangon	6:24:40 -	LMT	1880        # or Rangoon
-			6:24:40	-	RMT	1920        # Rangoon Mean Time?
+Zone	Asia/Yangon	6:24:47 -	LMT	1880        # or Rangoon
+			6:24:47	-	RMT	1920        # Rangoon local time
 			6:30	-	+0630	1942 May
 			9:00	-	+09	1945 May  3
 			6:30	-	+0630
@@ -317,7 +327,7 @@ Rule	PRC	1987	1991	-	Apr	Sun>=10	0:00	1:00	D
 #
 # From Jesper Nørgaard Welen (2006-07-14):
 # I have investigated the timezones around 1970 on the
-# http://www.astro.com/atlas site [with provinces and county
+# https://www.astro.com/atlas site [with provinces and county
 # boundaries summarized below]....  A few other exceptions were two
 # counties on the Sichuan side of the Xizang-Sichuan border,
 # counties Dege and Baiyu which lies on the Sichuan side and are
@@ -469,7 +479,7 @@ Rule	PRC	1987	1991	-	Apr	Sun>=10	0:00	1:00	D
 
 # From David Cochrane (2014-03-26):
 # Just a confirmation that Ürümqi time was implemented in Ürümqi on 1 Feb 1986:
-# http://content.time.com/time/magazine/article/0,9171,960684,00.html
+# https://content.time.com/time/magazine/article/0,9171,960684,00.html
 
 # From Luther Ma (2014-04-22):
 # I have interviewed numerous people of various nationalities and from
@@ -626,7 +636,7 @@ Zone	Asia/Hong_Kong	7:36:42 -	LMT	1904 Oct 30
 # (both in Okinawa) adopt the Western Standard Time which is based on
 # 120E. The adoption began from Jan 1, 1896. The original text can be
 # found on Wikisource:
-# http://ja.wikisource.org/wiki/標準時ニ關スル件_(公布時)
+# https://ja.wikisource.org/wiki/標準時ニ關スル件_(公布時)
 # ... This could be the first adoption of time zone in Taiwan, because
 # during the Qing Dynasty, it seems that there was no time zone
 # declared officially.
@@ -639,7 +649,7 @@ Zone	Asia/Hong_Kong	7:36:42 -	LMT	1904 Oct 30
 # territory, including later occupations, adopt Japan Central Time
 # (UTC+9). The adoption began on Oct 1, 1937. The original text can
 # be found on Wikisource:
-# http://ja.wikisource.org/wiki/明治二十八年勅令第百六十七號標準時ニ關スル件中改正ノ件
+# https://ja.wikisource.org/wiki/明治二十八年勅令第百六十七號標準時ニ關スル件中改正ノ件
 #
 # That is, the time zone of Taipei switched to UTC+9 on Oct 1, 1937.
 
@@ -775,6 +785,12 @@ Zone	Asia/Macau	7:34:20 -	LMT	1912 Jan  1
 # Looks like the time zone split in Cyprus went through last night.
 # http://cyprus-mail.com/2016/10/30/cyprus-new-division-two-time-zones-now-reality/
 
+# From Paul Eggert (2017-10-18):
+# Northern Cyprus will reinstate winter time on October 29, thus
+# staying in sync with the rest of Cyprus.  See: Anastasiou A.
+# Cyprus to remain united in time.  Cyprus Mail 2017-10-17.
+# https://cyprus-mail.com/2017/10/17/cyprus-remain-united-time/
+
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	Cyprus	1975	only	-	Apr	13	0:00	1:00	S
 Rule	Cyprus	1975	only	-	Oct	12	0:00	0	-
@@ -792,7 +808,8 @@ Zone	Asia/Nicosia	2:13:28 -	LMT	1921 Nov 14
 Zone	Asia/Famagusta	2:15:48	-	LMT	1921 Nov 14
 			2:00	Cyprus	EE%sT	1998 Sep
 			2:00	EUAsia	EE%sT	2016 Sep  8
-			3:00	-	+03
+			3:00	-	+03	2017 Oct 29 1:00u
+			2:00	EUAsia	EE%sT
 
 # Classically, Cyprus belongs to Asia; e.g. see Herodotus, Histories, I.72.
 # However, for various reasons many users expect to find it under Europe.
@@ -852,7 +869,7 @@ Zone	Asia/Tbilisi	2:59:11 -	LMT	1880
 
 # From João Carrascalão, brother of the former governor of East Timor, in
 # East Timor may be late for its millennium
-# <http://etan.org/et99c/december/26-31/30ETMAY.htm> (1999-12-26/31):
+# <https://etan.org/et99c/december/26-31/30ETMAY.htm> (1999-12-26/31):
 # Portugal tried to change the time forward in 1974 because the sun
 # rises too early but the suggestion raised a lot of problems with the
 # Timorese and I still don't think it would work today because it
@@ -880,21 +897,62 @@ Zone	Asia/Dili	8:22:20 -	LMT	1912 Jan  1
 # India
 
 # From Ian P. Beacock, in "A brief history of (modern) time", The Atlantic
-# http://www.theatlantic.com/technology/archive/2015/12/the-creation-of-modern-time/421419/
+# https://www.theatlantic.com/technology/archive/2015/12/the-creation-of-modern-time/421419/
 # (2015-12-22):
 # In January 1906, several thousand cotton-mill workers rioted on the
 # outskirts of Bombay....  They were protesting the proposed abolition of
 # local time in favor of Indian Standard Time....  Journalists called this
 # dispute the "Battle of the Clocks."  It lasted nearly half a century.
 
+# From Paul Eggert (2017-04-20):
+# Good luck trying to nail down old timekeeping records in India.
+# "... in the nineteenth century ... Madras Observatory took its magnetic
+# measurements on Göttingen time, its meteorological measurements on Madras
+# (local) time, dropped its time ball on Greenwich (ocean navigator's) time,
+# and distributed civil (local time)." -- Bartky IR. Selling the true time:
+# 19th-century timekeeping in america. Stanford U Press (2000), 247 note 19.
+# "A more potent cause of resistance to the general adoption of the present
+# standard time lies in the fact that it is Madras time.  The citizen of
+# Bombay, proud of being 'primus in Indis' and of Calcutta, equally proud of
+# his city being the Capital of India, and - for a part of the year - the Seat
+# of the Supreme Government, alike look down on Madras, and refuse to change
+# the time they are using, for that of what they regard as a benighted
+# Presidency; while Madras, having for long given the standard time to the
+# rest of India, would resist the adoption of any other Indian standard in its
+# place." -- Oldham RD. On Time in India: a suggestion for its improvement.
+# Proceedings of the Asiatic Society of Bengal (April 1899), 49-55.
+#
+# "In 1870 ... Madras time - 'now used by the telegraph and regulated from the
+# only government observatory' - was suggested as a standard railway time,
+# first to be adopted on the Great Indian Peninsular Railway (GIPR)....
+# Calcutta, Bombay, and Karachi, were to be allowed to continue with their
+# local time for civil purposes." - Prasad R. Tracks of Change: Railways and
+# Everyday Life in Colonial India. Cambridge University Press (2016), 145.
+#
+# Reed S, Low F. The Indian Year Book 1936-37. Bennett, Coleman, pp 27-8.
+# https://archive.org/details/in.ernet.dli.2015.282212
+# This lists +052110 as Madras local time used in railways, and says that on
+# 1906-01-01 railways and telegraphs in India switched to +0530.  Some
+# municipalities retained their former time, and the time in Calcutta
+# continued to depend on whether you were at the railway station or at
+# government offices.  Government time was at +055320 (according to Shanks) or
+# at +0554 (according to the Indian Year Book).  Railway time is more
+# appropriate for our purposes, as it was better documented, it is what we do
+# elsewhere (e.g., Europe/London before 1880), and after 1906 it was
+# consistent in the region now identified by Asia/Kolkata.  So, use railway
+# time for 1870-1941.  Shanks is our only (and dubious) source for the
+# 1941-1945 data.
+
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Asia/Kolkata	5:53:28 -	LMT	1880        # Kolkata
-			5:53:20	-	HMT	1941 Oct    # Howrah Mean Time?
-			6:30	-	+0630	1942 May 15
+Zone	Asia/Kolkata	5:53:28 -	LMT	1854 Jun 28 # Kolkata
+			5:53:20	-	HMT	1870	    # Howrah Mean Time?
+			5:21:10	-	MMT	1906 Jan  1 # Madras local time
+			5:30	-	IST	1941 Oct
+			5:30	1:00	+0630	1942 May 15
 			5:30	-	IST	1942 Sep
 			5:30	1:00	+0630	1945 Oct 15
 			5:30	-	IST
-# The following are like Asia/Kolkata:
+# Since 1970 the following are like Asia/Kolkata:
 #	Andaman Is
 #	Lakshadweep (Laccadive, Minicoy and Amindivi Is)
 #	Nicobar Is
@@ -1036,7 +1094,7 @@ Zone Asia/Jayapura	9:22:48 -	LMT	1932 Nov
 # From Reuters (2007-09-16), with a heads-up from Jesper Nørgaard Welen:
 # ... the Guardian Council ... approved a law on Sunday to re-introduce
 # daylight saving time ...
-# http://uk.reuters.com/article/oilRpt/idUKBLA65048420070916
+# https://uk.reuters.com/article/oilRpt/idUKBLA65048420070916
 #
 # From Roozbeh Pournader (2007-11-05):
 # This is quoted from Official Gazette of the Islamic Republic of
@@ -1135,7 +1193,7 @@ Zone	Asia/Tehran	3:25:44	-	LMT	1916
 # http://www.aswataliraq.info/look/article.tpl?id=2047&IdLanguage=17&IdPublication=4&NrArticle=71743&NrIssue=1&NrSection=10
 #
 # We have published a short article in English about the change:
-# http://www.timeanddate.com/news/time/iraq-dumps-daylight-saving.html
+# https://www.timeanddate.com/news/time/iraq-dumps-daylight-saving.html
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	Iraq	1982	only	-	May	1	0:00	1:00	D
@@ -1443,12 +1501,12 @@ Rule	Japan	1950	1951	-	May	Sun>=1	2:00	1:00	D
 # From Yu-Cheng Chuang (2013-07-12):
 # ...the Meiji Emperor announced Ordinance No. 167 of Meiji Year 28 "The clause
 # about standard time" ... The adoption began from Jan 1, 1896.
-# http://ja.wikisource.org/wiki/標準時ニ關スル件_(公布時)
+# https://ja.wikisource.org/wiki/標準時ニ關スル件_(公布時)
 #
 # ...the Showa Emperor announced Ordinance No. 529 of Showa Year 12 ... which
 # means the whole Japan territory, including later occupations, adopt Japan
 # Central Time (UTC+9). The adoption began on Oct 1, 1937.
-# http://ja.wikisource.org/wiki/明治二十八年勅令第百六十七號標準時ニ關スル件中改正ノ件
+# https://ja.wikisource.org/wiki/明治二十八年勅令第百六十七號標準時ニ關スル件中改正ノ件
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Asia/Tokyo	9:18:59	-	LMT	1887 Dec 31 15:00u
@@ -1510,7 +1568,7 @@ Zone	Asia/Tokyo	9:18:59	-	LMT	1887 Dec 31 15:00u
 # Official, in Arabic:
 # http://www.petra.gov.jo/public_news/Nws_NewsDetails.aspx?Menu_ID=&Site_Id=2&lang=1&NewsID=133230&CatID=14
 # ... Our background/permalink about it
-# http://www.timeanddate.com/news/time/jordan-reverses-dst-decision.html
+# https://www.timeanddate.com/news/time/jordan-reverses-dst-decision.html
 # ...
 # http://www.petra.gov.jo/Public_News/Nws_NewsDetails.aspx?lang=2&site_id=1&NewsID=133313&Type=P
 # ... says midnight for the coming one and 1:00 for the ones in the future
@@ -1868,9 +1926,9 @@ Zone	Asia/Bishkek	4:58:24 -	LMT	1924 May  2
 # between 1987 and 1988 ...
 
 # From Sanghyuk Jung (2014-10-29):
-# http://mm.icann.org/pipermail/tz/2014-October/021830.html
+# https://mm.icann.org/pipermail/tz/2014-October/021830.html
 # According to the Korean Wikipedia
-# http://ko.wikipedia.org/wiki/한국_표준시
+# https://ko.wikipedia.org/wiki/한국_표준시
 # [oldid=12896437 2014-09-04 08:03 UTC]
 # DST in Republic of Korea was as follows....  And I checked old
 # newspapers in Korean, all articles correspond with data in Wikipedia.
@@ -2092,7 +2150,7 @@ Zone	Indian/Maldives	4:54:00 -	LMT	1880 # Male
 # +08:00 instead. Different sources appear to disagree with the tz
 # database on this, e.g.:
 #
-# http://www.timeanddate.com/worldclock/city.html?n=1026
+# https://www.timeanddate.com/worldclock/city.html?n=1026
 # http://www.worldtimeserver.com/current_time_in_MN.aspx
 #
 # both say GMT+08:00.
@@ -2222,7 +2280,7 @@ Zone	Asia/Kathmandu	5:41:16 -	LMT	1920
 # help reduce load shedding by approving the closure of commercial centres at
 # 9pm and moving clocks forward by one hour for the next three months. ...."
 #
-# http://www.worldtimezone.net/dst_news/dst_news_pakistan01.html
+# http://www.worldtimezone.com/dst_news/dst_news_pakistan01.html
 # http://www.dailytimes.com.pk/default.asp?page=2008%5C05%5C15%5Cstory_15-5-2008_pg1_4
 
 # From Arthur David Olson (2008-05-19):
@@ -2288,7 +2346,7 @@ Zone	Asia/Kathmandu	5:41:16 -	LMT	1920
 #
 # We have confirmed this year's end date with both with the Ministry of
 # Water and Power and the Pakistan Electric Power Company:
-# http://www.timeanddate.com/news/time/pakistan-ends-dst09.html
+# https://www.timeanddate.com/news/time/pakistan-ends-dst09.html
 
 # From Christoph Göhre (2009-10-01):
 # [T]he German Consulate General in Karachi reported me today that Pakistan
@@ -2470,7 +2528,7 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 #
 # We are not sure if Gaza will do the same, last year they had a different
 # end date, we will keep this page updated:
-# http://www.timeanddate.com/news/time/westbank-gaza-dst-2009.html
+# https://www.timeanddate.com/news/time/westbank-gaza-dst-2009.html
 
 # From Alexander Krivenyshev (2009-09-02):
 # Seems that Gaza Strip will go back to Winter Time same date as West Bank.
@@ -2508,7 +2566,7 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 # the clocks were set back one hour at 2010-08-11 00:00:00 local time in
 # Gaza and the West Bank.
 # Some more background info:
-# http://www.timeanddate.com/news/time/westbank-gaza-end-dst-2010.html
+# https://www.timeanddate.com/news/time/westbank-gaza-end-dst-2010.html
 
 # From Steffen Thorsen (2011-08-26):
 # Gaza and the West Bank did go back to standard time in the beginning of
@@ -2518,7 +2576,7 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 #
 # http://www.maannews.net/eng/ViewDetails.aspx?ID=416217
 # Additional info:
-# http://www.timeanddate.com/news/time/palestine-dst-2011.html
+# https://www.timeanddate.com/news/time/palestine-dst-2011.html
 
 # From Alexander Krivenyshev (2011-08-27):
 # According to the article in The Jerusalem Post:
@@ -2528,7 +2586,7 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 # The Hamas government said on Saturday that it won't observe summertime after
 # the Muslim feast of Id al-Fitr, which begins on Tuesday..."
 # ...
-# http://www.jpost.com/MiddleEast/Article.aspx?id=235650
+# https://www.jpost.com/MiddleEast/Article.aspx?id=235650
 # http://www.worldtimezone.com/dst_news/dst_news_gazastrip05.html
 # The rules for Egypt are stolen from the 'africa' file.
 
@@ -2549,7 +2607,7 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 # http://safa.ps/details/news/74352/%D8%A8%D8%AF%D8%A1-%D8%A7%D9%84%D8%AA%D9%88%D9%82%D9%8A%D8%AA-%D8%A7%D9%84%D8%B5%D9%8A%D9%81%D9%8A-%D8%A8%D8%A7%D9%84%D8%B6%D9%81%D8%A9-%D9%88%D8%BA%D8%B2%D8%A9-%D9%84%D9%8A%D9%84%D8%A9-%D8%A7%D9%84%D8%AC%D9%85%D8%B9%D8%A9.html
 #
 # Our brief summary:
-# http://www.timeanddate.com/news/time/gaza-west-bank-dst-2012.html
+# https://www.timeanddate.com/news/time/gaza-west-bank-dst-2012.html
 
 # From Steffen Thorsen (2013-03-26):
 # The following news sources tells that Palestine will "start daylight saving
@@ -2569,11 +2627,11 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 
 # From Steffen Thorsen (2015-03-03):
 # Sources such as http://www.alquds.com/news/article/view/id/548257
-# and http://www.raya.ps/ar/news/890705.html say Palestine areas will
+# and https://www.raya.ps/ar/news/890705.html say Palestine areas will
 # start DST on 2015-03-28 00:00 which is one day later than expected.
 #
 # From Paul Eggert (2015-03-03):
-# http://www.timeanddate.com/time/change/west-bank/ramallah?year=2014
+# https://www.timeanddate.com/time/change/west-bank/ramallah?year=2014
 # says that the fall 2014 transition was Oct 23 at 24:00.
 
 # From Hannah Kreitem (2016-03-09):
@@ -2597,8 +2655,8 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 #
 # From Paul Eggert (2016-10-19):
 # It's also consistent with predictions in the following URLs today:
-# http://www.timeanddate.com/time/change/gaza-strip/gaza
-# http://www.timeanddate.com/time/change/west-bank/hebron
+# https://www.timeanddate.com/time/change/gaza-strip/gaza
+# https://www.timeanddate.com/time/change/west-bank/hebron
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule EgyptAsia	1957	only	-	May	10	0:00	1:00	S
@@ -2661,7 +2719,7 @@ Zone	Asia/Hebron	2:20:23	-	LMT	1900 Oct
 # Philippines, issued a proclamation announcing that 1844-12-30 was to
 # be immediately followed by 1845-01-01; see R.H. van Gent's
 # History of the International Date Line
-# http://www.staff.science.uu.nl/~gent0113/idl/idl_philippines.htm
+# https://www.staff.science.uu.nl/~gent0113/idl/idl_philippines.htm
 # The rest of the data entries are from Shanks & Pottenger.
 
 # From Jesper Nørgaard Welen (2006-04-26):
@@ -2925,7 +2983,7 @@ Rule	Syria	2007	only	-	Nov	 Fri>=1	0:00	0	-
 # We have not found any sources saying anything about when DST ends this year.
 #
 # Our summary
-# http://www.timeanddate.com/news/time/syria-dst-starts-march-27-2009.html
+# https://www.timeanddate.com/news/time/syria-dst-starts-march-27-2009.html
 
 # From Steffen Thorsen (2009-10-27):
 # The Syrian Arab News Network on 2009-09-29 reported that Syria will
@@ -2952,7 +3010,7 @@ Rule	Syria	2007	only	-	Nov	 Fri>=1	0:00	0	-
 # http://www.sana.sy/ara/2/2012/03/26/408215.htm
 #
 # Our brief summary:
-# http://www.timeanddate.com/news/time/syria-dst-2012.html
+# https://www.timeanddate.com/news/time/syria-dst-2012.html
 
 # From Arthur David Olson (2012-03-27):
 # Assume last Friday in March going forward XXX.
@@ -3035,7 +3093,7 @@ Zone	Asia/Tashkent	4:37:11 -	LMT	1924 May  2
 # is quoted verbatim in:
 # http://www.thoigian.com.vn/?mPage=P80D01
 # is translated by Brian Inglis in:
-# http://mm.icann.org/pipermail/tz/2014-October/021654.html
+# https://mm.icann.org/pipermail/tz/2014-October/021654.html
 # and is the basis for the information below.
 #
 # The 1906 transition was effective July 1 and standardized Indochina to
diff --git a/contrib/tzdata/australasia b/contrib/tzdata/australasia
index d389ae134ab7..5f7c86dda660 100644
--- a/contrib/tzdata/australasia
+++ b/contrib/tzdata/australasia
@@ -293,7 +293,7 @@ Zone	Indian/Cocos	6:27:40	-	LMT	1900
 # http://www.fiji.gov.fj/index.php?option=com_content&view=article&id=1096:3310-cabinet-approves-change-in-daylight-savings-dates&catid=49:cabinet-releases&Itemid=166
 #
 # A bit more background info here:
-# http://www.timeanddate.com/news/time/fiji-dst-ends-march-2010.html
+# https://www.timeanddate.com/news/time/fiji-dst-ends-march-2010.html
 
 # From Alexander Krivenyshev (2010-10-24):
 # According to Radio Fiji and Fiji Times online, Fiji will end DST 3
@@ -357,9 +357,12 @@ Zone	Indian/Cocos	6:27:40	-	LMT	1900
 # clocks go forward an hour at 2am to 3am....  Daylight Saving will
 # end at 3.00am on Sunday 15th January 2017."
 
-# From Paul Eggert (2016-10-03):
-# For now, guess DST from 02:00 the first Sunday in November to
-# 03:00 the third Sunday in January.  Although ad hoc, it matches
+# From Paul Eggert (2017-08-21):
+# Dominic Fok writes (2017-08-20) that DST ends 2018-01-14, citing
+# Extraordinary Government of Fiji Gazette Supplement No. 21 (2017-08-27),
+# [Legal Notice No. 41] of an order of the previous day by J Usamate.
+# For now, guess DST from 02:00 the first Sunday in November to 03:00
+# the first Sunday on or after January 14.  Although ad hoc, it matches
 # transitions since late 2014 and seems more likely to match future
 # practice than guessing no DST.
 
@@ -373,7 +376,7 @@ Rule	Fiji	2011	only	-	Mar	Sun>=1	3:00	0	-
 Rule	Fiji	2012	2013	-	Jan	Sun>=18	3:00	0	-
 Rule	Fiji	2014	only	-	Jan	Sun>=18	2:00	0	-
 Rule	Fiji	2014	max	-	Nov	Sun>=1	2:00	1:00	S
-Rule	Fiji	2015	max	-	Jan	Sun>=15	3:00	0	-
+Rule	Fiji	2015	max	-	Jan	Sun>=14	3:00	0	-
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Pacific/Fiji	11:55:44 -	LMT	1915 Oct 26 # Suva
 			12:00	Fiji	+12/+13
@@ -557,7 +560,7 @@ Zone Pacific/Port_Moresby 9:48:40 -	LMT	1880
 # The World War II entries below are instead based on Arawa-Kieta.
 # The Japanese occupied Kieta in July 1942,
 # according to the Pacific War Online Encyclopedia
-# http://pwencycl.kgbudge.com/B/o/Bougainville.htm
+# https://pwencycl.kgbudge.com/B/o/Bougainville.htm
 # and seem to have controlled it until their 1945-08-21 surrender.
 #
 # The Autonomous Region of Bougainville switched from UT +10 to +11
@@ -579,7 +582,7 @@ Zone Pacific/Pitcairn	-8:40:20 -	LMT	1901        # Adamstown
 			-8:00	-	-08
 
 # American Samoa
-Zone Pacific/Pago_Pago	 12:37:12 -	LMT	1879 Jul  5
+Zone Pacific/Pago_Pago	 12:37:12 -	LMT	1892 Jul  5
 			-11:22:48 -	LMT	1911
 			-11:00	-	SST	            # S=Samoa
 Link Pacific/Pago_Pago Pacific/Midway # in US minor outlying islands
@@ -595,7 +598,7 @@ Link Pacific/Pago_Pago Pacific/Midway # in US minor outlying islands
 # Sunday of April 2011."
 #
 # Background info:
-# http://www.timeanddate.com/news/time/samoa-dst-plan-2009.html
+# https://www.timeanddate.com/news/time/samoa-dst-plan-2009.html
 #
 # Samoa's Daylight Saving Time Act 2009 is available here, but does not
 # contain any dates:
@@ -659,7 +662,7 @@ Rule	WS	2011	only	-	Sep	lastSat	3:00	1	D
 Rule	WS	2012	max	-	Apr	Sun>=1	4:00	0	S
 Rule	WS	2012	max	-	Sep	lastSun	3:00	1	D
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone Pacific/Apia	 12:33:04 -	LMT	1879 Jul  5
+Zone Pacific/Apia	 12:33:04 -	LMT	1892 Jul  5
 			-11:26:56 -	LMT	1911
 			-11:30	-	-1130	1950
 			-11:00	WS	-11/-10	2011 Dec 29 24:00
@@ -686,7 +689,7 @@ Zone Pacific/Guadalcanal 10:39:48 -	LMT	1912 Oct # Honiara
 # From Paul Eggert (2012-07-25)
 # A Google Books snippet of Appendix to the Journals of the House of
 # Representatives of New Zealand, Session 1948,
-# <http://books.google.com/books?id=ZaVCAQAAIAAJ>, page 65, says Tokelau
+# <https://books.google.com/books?id=ZaVCAQAAIAAJ>, page 65, says Tokelau
 # was "11 hours slow on G.M.T."  Go with Thorsen and assume Shanks & Pottenger
 # are off by an hour starting in 1901.
 
@@ -701,8 +704,8 @@ Rule	Tonga	1999	only	-	Oct	 7	2:00s	1:00	S
 Rule	Tonga	2000	only	-	Mar	19	2:00s	0	-
 Rule	Tonga	2000	2001	-	Nov	Sun>=1	2:00	1:00	S
 Rule	Tonga	2001	2002	-	Jan	lastSun	2:00	0	-
-Rule	Tonga	2016	max	-	Nov	Sun>=1	2:00	1:00	S
-Rule	Tonga	2017	max	-	Jan	Sun>=15	3:00	0	-
+Rule	Tonga	2016	only	-	Nov	Sun>=1	2:00	1:00	S
+Rule	Tonga	2017	only	-	Jan	Sun>=15	3:00	0	-
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone Pacific/Tongatapu	12:19:20 -	LMT	1901
 			12:20	-	+1220	1941
@@ -756,7 +759,7 @@ Zone Pacific/Funafuti	11:56:52 -	LMT	1901
 # Operation Fishbowl shot (Tightrope, 1962-11-04).... [See] Herman Hoerlin,
 # "The United States High-Altitude Test Experience: A Review Emphasizing the
 # Impact on the Environment", Los Alamos LA-6405, Oct 1976.
-# http://www.fas.org/sgp/othergov/doe/lanl/docs1/00322994.pdf
+# https://www.fas.org/sgp/othergov/doe/lanl/docs1/00322994.pdf
 # See the table on page 4 where he lists GMT and local times for the tests; a
 # footnote for the JI tests reads that local time is "JI time = Hawaii Time
 # Minus One Hour".
@@ -822,7 +825,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 #
 # For data circa 1899, a common source is:
 # Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94.
-# http://www.jstor.org/stable/1774359
+# https://www.jstor.org/stable/1774359
 #
 # A reliable and entertaining source about time zones is
 # Derek Howse, Greenwich time and longitude, Philip Wilson Publishers (1997).
@@ -969,7 +972,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 #   AEST ACST AWST AEDT ACDT
 #
 #   Parliamentary Library (2008-11-10)
-#   http://www.aph.gov.au/binaries/library/pubs/rp/2008-09/09rp14.pdf
+#   https://www.aph.gov.au/binaries/library/pubs/rp/2008-09/09rp14.pdf
 #   EST CST WST preferred for standard time; AEST AEDT ACST ACDT also used
 #
 #   The Transport Safety Bureau has an extensive series of accident reports,
@@ -1005,13 +1008,13 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 #
 # NSW (including LHI and Broken Hill):
 # Standard Time Act 1987 (updated 1995-04-04)
-# http://www.austlii.edu.au/au/legis/nsw/consol_act/sta1987137/index.html
+# https://www.austlii.edu.au/au/legis/nsw/consol_act/sta1987137/index.html
 # ACT
 # Standard Time and Summer Time Act 1972
-# http://www.austlii.edu.au/au/legis/act/consol_act/stasta1972279/index.html
+# https://www.austlii.edu.au/au/legis/act/consol_act/stasta1972279/index.html
 # SA
 # Standard Time Act, 1898
-# http://www.austlii.edu.au/au/legis/sa/consol_act/sta1898137/index.html
+# https://www.austlii.edu.au/au/legis/sa/consol_act/sta1898137/index.html
 
 # From David Grosz (2005-06-13):
 # It was announced last week that Daylight Saving would be extended by
@@ -1306,7 +1309,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # http://abc.net.au/news/regionals/neweng/monthly/regeng-22jul1999-1.htm
 # (1999-07-22).  For now, we'll wait to see if this really happens.
 #
-# Victoria will following NSW.  See:
+# Victoria will follow NSW.  See:
 # Vic to extend daylight saving (1999-07-28)
 # http://abc.net.au/local/news/olympics/1999/07/item19990728112314_1.htm
 #
@@ -1409,7 +1412,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # the ACT for all 52 weeks of the year...
 #
 # We have a wrap-up here:
-# http://www.timeanddate.com/news/time/south-australia-extends-dst.html
+# https://www.timeanddate.com/news/time/south-australia-extends-dst.html
 ###############################################################################
 
 # New Zealand
@@ -1463,7 +1466,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # From Paul Eggert (2014-07-14):
 # Chatham Island time was formally standardized on 1957-01-01 by
 # New Zealand's Standard Time Amendment Act 1956 (1956-10-26).
-# http://www.austlii.edu.au/nz/legis/hist_act/staa19561956n100244.pdf
+# https://www.austlii.edu.au/nz/legis/hist_act/staa19561956n100244.pdf
 # According to Google Books snippet view, a speaker in the New Zealand
 # parliamentary debates in 1956 said "Clause 78 makes provision for standard
 # time in the Chatham Islands.  The time there is 45 minutes in advance of New
@@ -1578,7 +1581,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # the Norfolk Island Museum and the Australian Bureau of Meteorology's
 # Norfolk Island station, and found no record of Norfolk observing DST
 # other than in 1974/5.  See:
-# http://www.timeanddate.com/time/australia/norfolk-island.html
+# https://www.timeanddate.com/time/australia/norfolk-island.html
 
 # Pitcairn
 
@@ -1606,11 +1609,13 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 
 # (Western) Samoa and American Samoa
 
-# Howse writes (p 153, citing p 10 of the 1883-11-18 New York Herald)
-# that in 1879 the King of Samoa decided to change
+# Howse writes (p 153) that after the 1879 standardization on Antipodean
+# time by the British governor of Fiji, the King of Samoa decided to change
 # "the date in his kingdom from the Antipodean to the American system,
 # ordaining - by a masterpiece of diplomatic flattery - that
 # the Fourth of July should be celebrated twice in that year."
+# This happened in 1892, according to the Evening News (Sydney) of 1892-07-20.
+# https://www.staff.science.uu.nl/~gent0113/idl/idl.htm
 
 # Although Shanks & Pottenger says they both switched to UT -11:30
 # in 1911, and to -11 in 1950. many earlier sources give -11
@@ -1621,6 +1626,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # day in 2011.  Assume also that the Samoas follow the US and New
 # Zealand's "ST"/"DT" style of daylight-saving abbreviations.
 
+
 # Tonga
 
 # From Paul Eggert (1996-01-22):
@@ -1715,6 +1721,15 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # Assume Tonga will observe DST from the first Sunday in November at 02:00
 # through the third Sunday in January at 03:00, like Fiji, for now.
 
+# From David Wade (2017-10-18):
+# In August government was disolved by the King.  The current prime minister
+# continued in office in care taker mode.  It is easy to see that few
+# decisions will be made until elections 16th November.
+#
+# From Paul Eggert (2017-10-18):
+# For now, guess that DST is discontinued.  That's what the IATA is guessing.
+
+
 # Wake
 
 # From Vernice Anderson, Personal Secretary to Philip Jessup,
@@ -1727,7 +1742,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # making calculation of time in Washington difficult if not almost
 # impossible.
 #
-# http://www.trumanlibrary.org/wake/meeting.htm
+# https://www.trumanlibrary.org/oralhist/andrsonv.htm
 
 # From Paul Eggert (2003-03-23):
 # We have no other report of DST in Wake Island, so omit this info for now.
@@ -1755,7 +1770,7 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # an international standard, there are some places on the high seas where the
 # correct date is ambiguous.
 
-# From Wikipedia <http://en.wikipedia.org/wiki/Time_zone> (2005-08-31):
+# From Wikipedia <https://en.wikipedia.org/wiki/Time_zone> (2005-08-31):
 # Before 1920, all ships kept local apparent time on the high seas by setting
 # their clocks at night or at the morning sight so that, given the ship's
 # speed and direction, it would be 12 o'clock when the Sun crossed the ship's
diff --git a/contrib/tzdata/backward b/contrib/tzdata/backward
index 09f2a31b685d..2141f0d5798f 100644
--- a/contrib/tzdata/backward
+++ b/contrib/tzdata/backward
@@ -61,7 +61,9 @@ Link	America/Sao_Paulo	Brazil/East
 Link	America/Manaus		Brazil/West
 Link	America/Halifax		Canada/Atlantic
 Link	America/Winnipeg	Canada/Central
-Link	America/Regina		Canada/East-Saskatchewan
+# This line is commented out, as the name exceeded the 14-character limit
+# and was an unused misnomer.
+#Link	America/Regina		Canada/East-Saskatchewan
 Link	America/Toronto		Canada/Eastern
 Link	America/Edmonton	Canada/Mountain
 Link	America/St_Johns	Canada/Newfoundland
diff --git a/contrib/tzdata/backzone b/contrib/tzdata/backzone
index 9ce78316c2b3..32bd0f106155 100644
--- a/contrib/tzdata/backzone
+++ b/contrib/tzdata/backzone
@@ -181,7 +181,7 @@ Zone	Africa/Lome	0:04:52 -	LMT	1893
 # with the date that it took effect, namely 1912-01-01.
 #
 Zone	Africa/Luanda	0:52:56	-	LMT	1892
-			0:52:04	-	+005204	1912 Jan  1
+			0:52:04	-	LMT	1912 Jan  1 # Luanda Mean Time?
 			1:00	-	WAT
 
 # Democratic Republic of the Congo (east)
@@ -540,10 +540,10 @@ Zone	Europe/Belfast	-0:23:40 -	LMT	1880 Aug  2
 
 # Guernsey
 # Data from Joseph S. Myers
-# http://mm.icann.org/pipermail/tz/2013-September/019883.html
+# https://mm.icann.org/pipermail/tz/2013-September/019883.html
 # References to be added
-# LMT Location - 49.27N -2.33E - St.Peter Port
-Zone	Europe/Guernsey	-0:09:19 -	LMT	1913 Jun 18
+# LMT is for Town Church, St. Peter Port, 49 degrees 27'17"N 2 degrees 32'10"W
+Zone	Europe/Guernsey	-0:10:09 -	LMT	1913 Jun 18
 			 0:00	GB-Eire	%s	1940 Jul  2
 			 1:00	C-Eur	CE%sT	1945 May  8
 			 0:00	GB-Eire	%s	1968 Oct 27
@@ -555,11 +555,11 @@ Zone	Europe/Guernsey	-0:09:19 -	LMT	1913 Jun 18
 #
 # From Lester Caine (2013-09-04):
 # The Isle of Man legislation is now on-line at
-# <http://www.legislation.gov.im>, starting with the original Statutory
+# <https://www.legislation.gov.im>, starting with the original Statutory
 # Time Act in 1883 and including additional confirmation of some of
 # the dates of the 'Summer Time' orders originating at
 # Westminster.  There is a little uncertainty as to the starting date
-# of the first summer time in 1916 which may have be announced a
+# of the first summer time in 1916 which may have been announced a
 # couple of days late.  There is still a substantial number of
 # documents to work through, but it is thought that every GB change
 # was also implemented on the island.
@@ -574,10 +574,10 @@ Zone Europe/Isle_of_Man	-0:17:55 -	LMT	1883 Mar 30  0:00s
 
 # Jersey
 # Data from Joseph S. Myers
-# http://mm.icann.org/pipermail/tz/2013-September/019883.html
+# https://mm.icann.org/pipermail/tz/2013-September/019883.html
 # References to be added
-# LMT Location - 49.187N -2.107E - St. Helier
-Zone	Europe/Jersey	-0:08:25 -	LMT	1898 Jun 11 16:00u
+# LMT is for Parish Church, St. Helier, 49 degrees 11'0.57"N 2 degrees 6'24.33"W
+Zone	Europe/Jersey	-0:08:26 -	LMT	1898 Jun 11 16:00u
 			 0:00	GB-Eire	%s	1940 Jul  2
 			 1:00	C-Eur	CE%sT	1945 May  8
 			 0:00	GB-Eire	%s	1968 Oct 27
diff --git a/contrib/tzdata/calendars b/contrib/tzdata/calendars
new file mode 100644
index 000000000000..8bc70626eb5a
--- /dev/null
+++ b/contrib/tzdata/calendars
@@ -0,0 +1,173 @@
+----- Calendrical issues -----
+
+As mentioned in Theory.html, although calendrical issues are out of
+scope for tzdb, they indicate the sort of problems that we would run
+into if we extended tzdb further into the past.  The following
+information and sources go beyond Theory.html's brief discussion.
+They sometimes disagree.
+
+
+France
+
+Gregorian calendar adopted 1582-12-20.
+French Revolutionary calendar used 1793-11-24 through 1805-12-31,
+and (in Paris only) 1871-05-06 through 1871-05-23.
+
+
+Russia
+
+From Chris Carrier (1996-12-02):
+On 1929-10-01 the Soviet Union instituted an "Eternal Calendar"
+with 30-day months plus 5 holidays, with a 5-day week.
+On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the
+Gregorian calendar while retaining the 6-day week; on 1940-06-27 it
+reverted to the 7-day week.  With the 6-day week the usual days
+off were the 6th, 12th, 18th, 24th and 30th of the month.
+(Source: Evitiar Zerubavel, _The Seven Day Circle_)
+
+
+Mark Brader reported a similar story in "The Book of Calendars", edited
+by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377.  But:
+
+From: Petteri Sulonen (via Usenet)
+Date: 14 Jan 1999 00:00:00 GMT
+...
+
+If your source is correct, how come documents between 1929 and 1940 were
+still dated using the conventional, Gregorian calendar?
+
+I can post a scan of a document dated December 1, 1934, signed by
+Yenukidze, the secretary, on behalf of Kalinin, the President of the
+Executive Committee of the Supreme Soviet, if you like.
+
+
+
+Sweden (and Finland)
+
+From: Mark Brader
+Subject: Re: Gregorian reform - a part of locale?
+<news:1996Jul6.012937.29190@sq.com>
+Date: 1996-07-06
+
+In 1700, Denmark made the transition from Julian to Gregorian.  Sweden
+decided to *start* a transition in 1700 as well, but rather than have one of
+those unsightly calendar gaps :-), they simply decreed that the next leap
+year after 1696 would be in 1744 - putting the whole country on a calendar
+different from both Julian and Gregorian for a period of 40 years.
+
+However, in 1704 something went wrong and the plan was not carried through;
+they did, after all, have a leap year that year.  And one in 1708.  In 1712
+they gave it up and went back to Julian, putting 30 days in February that
+year!...
+
+Then in 1753, Sweden made the transition to Gregorian in the usual manner,
+getting there only 13 years behind the original schedule.
+
+(A previous posting of this story was challenged, and Swedish readers
+produced the following references to support it: "Tideräkning och historia"
+by Natanael Beckman (1924) and "Tid, en bok om tideräkning och
+kalenderväsen" by Lars-Olof Lodén (1968).
+
+
+Grotefend's data
+
+From: "Michael Palmer" [with one obvious typo fixed]
+Subject: Re: Gregorian Calendar (was Re: Another FHC related question
+Newsgroups: soc.genealogy.german
+Date: Tue, 9 Feb 1999 02:32:48 -800
+...
+
+The following is a(n incomplete) listing, arranged chronologically, of
+European states, with the date they converted from the Julian to the
+Gregorian calendar:
+
+04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman
+                 Catholics and Danzig only)
+09/20 Dec 1582 - France, Lorraine
+
+21 Dec 1582/
+   01 Jan 1583 - Holland, Brabant, Flanders, Hennegau
+10/21 Feb 1583 - bishopric of Liege (Lüttich)
+13/24 Feb 1583 - bishopric of Augsburg
+04/15 Oct 1583 - electorate of Trier
+05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg,
+                 Salzburg, Brixen
+13/24 Oct 1583 - Austrian Oberelsaß and Breisgau
+20/31 Oct 1583 - bishopric of Basel
+02/13 Nov 1583 - duchy of Jülich-Berg
+02/13 Nov 1583 - electorate and city of Köln
+04/15 Nov 1583 - bishopric of Würzburg
+11/22 Nov 1583 - electorate of Mainz
+16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden
+17/28 Nov 1583 - bishopric of Münster and duchy of Cleve
+14/25 Dec 1583 - Steiermark
+
+06/17 Jan 1584 - Austria and Bohemia
+11/22 Jan 1584 - Lucerne, Uri, Schwyz, Zug, Freiburg, Solothurn
+12/23 Jan 1584 - Silesia and the Lausitz
+22 Jan/
+   02 Feb 1584 - Hungary (legally on 21 Oct 1587)
+      Jun 1584 - Unterwalden
+01/12 Jul 1584 - duchy of Westfalen
+
+16/27 Jun 1585 - bishopric of Paderborn
+
+14/25 Dec 1590 - Transylvania
+
+22 Aug/
+   02 Sep 1612 - duchy of Prussia
+
+13/24 Dec 1614 - Pfalz-Neuburg
+
+          1617 - duchy of Kurland (reverted to the Julian calendar in
+                 1796)
+
+          1624 - bishopric of Osnabrück
+
+          1630 - bishopric of Minden
+
+15/26 Mar 1631 - bishopric of Hildesheim
+
+          1655 - Kanton Wallis
+
+05/16 Feb 1682 - city of Strassburg
+
+18 Feb/
+   01 Mar 1700 - Protestant Germany (including Swedish possessions in
+                 Germany), Denmark, Norway
+30 Jun/
+   12 Jul 1700 - Gelderland, Zutphen
+10 Nov/
+   12 Dec 1700 - Utrecht, Overijssel
+
+31 Dec 1700/
+   12 Jan 1701 - Friesland, Groningen, Zürich, Bern, Basel, Geneva,
+                 Turgau, and Schaffhausen
+
+          1724 - Glarus, Appenzell, and the city of St. Gallen
+
+01 Jan 1750    - Pisa and Florence
+
+02/14 Sep 1752 - Great Britain
+
+17 Feb/
+   01 Mar 1753 - Sweden
+
+1760-1812      - Graubünden
+
+The Russian empire (including Finland and the Baltic states) did not
+convert to the Gregorian calendar until the Soviet revolution of 1917.
+
+Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen
+Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend
+(Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28.
+
+-----
+
+This file is in the public domain, so clarified as of 2009-05-17 by
+Arthur David Olson.
+
+-----
+Local Variables:
+coding: utf-8
+End:
diff --git a/contrib/tzdata/checklinks.awk b/contrib/tzdata/checklinks.awk
index 5b3e1571d9f4..f30901086536 100644
--- a/contrib/tzdata/checklinks.awk
+++ b/contrib/tzdata/checklinks.awk
@@ -9,7 +9,7 @@ BEGIN {
     Zone = "\n"
 }
 
-/^Zone/ {
+/^Z/ {
     if (defined[$2]) {
 	if (defined[$2] == Zone) {
 	    printf "%s: Zone has duplicate definition\n", $2
@@ -21,7 +21,7 @@ BEGIN {
     defined[$2] = Zone
 }
 
-/^Link/ {
+/^L/ {
     if (defined[$3]) {
 	if (defined[$3] == Zone) {
 	    printf "%s: Link with same name as Zone\n", $3
diff --git a/contrib/tzdata/europe b/contrib/tzdata/europe
index 558b9f168f36..5b3b4e52fa44 100644
--- a/contrib/tzdata/europe
+++ b/contrib/tzdata/europe
@@ -37,14 +37,14 @@
 #	[PDF] (1914-03)
 #
 #	Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94
-#	<http://www.jstor.org/stable/1774359>.  He writes:
+#	<https://www.jstor.org/stable/1774359>.  He writes:
 #	"It is requested that corrections and additions to these tables
 #	may be sent to Mr. John Milne, Royal Geographical Society,
 #	Savile Row, London."  Nowadays please email them to tz@iana.org.
 #
 #	Byalokoz EL. New Counting of Time in Russia since July 1, 1919.
 #	This Russian-language source was consulted by Vladimir Karpinsky; see
-#	http://mm.icann.org/pipermail/tz/2014-August/021320.html
+#	https://mm.icann.org/pipermail/tz/2014-August/021320.html
 #	The full Russian citation is:
 #	Бялокоз, Евгений Людвигович. Новый счет времени в течении суток
 #	введенный декретом Совета народных комиссаров для всей России с 1-го
@@ -187,7 +187,7 @@
 # foundations of civilization throughout the world.
 #	-- "A Silent Toast to William Willett", Pictorial Weekly;
 #	republished in Finest Hour (Spring 2002) 1(114):26
-#	http://www.winstonchurchill.org/images/finesthour/Vol.01%20No.114.pdf
+#	https://www.winstonchurchill.org/publications/finest-hour/finest-hour-114/a-silent-toast-to-william-willett-by-winston-s-churchill
 
 # From Paul Eggert (2015-08-08):
 # The OED Supplement says that the English originally said "Daylight Saving"
@@ -225,8 +225,8 @@
 # official designation; the reply of the 21st was that there wasn't
 # but he couldn't think of anything better than the "Double British
 # Summer Time" that the BBC had been using informally.
-# http://www.polyomino.org.uk/british-time/bbc-19410418.png
-# http://www.polyomino.org.uk/british-time/ho-19410421.png
+# https://www.polyomino.org.uk/british-time/bbc-19410418.png
+# https://www.polyomino.org.uk/british-time/ho-19410421.png
 
 # From Sir Alexander Maxwell in the above-mentioned letter (1941-04-21):
 # [N]o official designation has as far as I know been adopted for the time
@@ -243,13 +243,13 @@
 # the history of summer time legislation in the United Kingdom.
 # Since 1998 Joseph S. Myers has been updating
 # and extending this list, which can be found in
-# http://www.polyomino.org.uk/british-time/
+# https://www.polyomino.org.uk/british-time/
 
 # From Joseph S. Myers (1998-01-06):
 #
 # The legal time in the UK outside of summer time is definitely GMT, not UTC;
 # see Lord Tanlaw's speech
-# http://www.publications.parliament.uk/pa/ld199798/ldhansrd/vo970611/text/70611-10.htm#70611-10_head0
+# https://www.publications.parliament.uk/pa/ld199798/ldhansrd/vo970611/text/70611-10.htm#70611-10_head0
 # (Lords Hansard 11 June 1997 columns 964 to 976).
 
 # From Paul Eggert (2006-03-22):
@@ -295,7 +295,7 @@
 # Irish 'public feeling (was) outraged by forcing of English time on us'."
 # -- Parsons M. Dublin lost its time zone - and 25 minutes - after 1916 Rising.
 # Irish Times 2014-10-27.
-# http://www.irishtimes.com/news/politics/dublin-lost-its-time-zone-and-25-minutes-after-1916-rising-1.1977411
+# https://www.irishtimes.com/news/politics/dublin-lost-its-time-zone-and-25-minutes-after-1916-rising-1.1977411
 
 # From Joseph S. Myers (2005-01-26):
 # Irish laws are available online at <http://www.irishstatutebook.ie>.
@@ -348,6 +348,12 @@
 # Justice (tel +353 1 678 9711) who confirmed to me that the correct name is
 # "Irish Summer Time", abbreviated to "IST".
 
+# Michael Deckers (2017-06-01) gave the following URLs for Ireland's
+# Summer Time Act, 1925 and Summer Time Orders, 1926 and 1947:
+# http://www.irishstatutebook.ie/eli/1925/act/8/enacted/en/print.html
+# http://www.irishstatutebook.ie/eli/1926/sro/919/made/en/print.html
+# http://www.irishstatutebook.ie/eli/1947/sro/71/made/en/print.html
+
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 # Summer Time Act, 1916
 Rule	GB-Eire	1916	only	-	May	21	2:00s	1:00	BST
@@ -472,14 +478,14 @@ Link	Europe/London	Europe/Isle_of_Man
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Europe/Dublin	-0:25:00 -	LMT	1880 Aug  2
-			-0:25:21 -	DMT	1916 May 21  2:00 # Dublin MT
+			-0:25:21 -	DMT	1916 May 21  2:00s # Dublin MT
 			-0:25:21 1:00	IST	1916 Oct  1  2:00s
 			 0:00	GB-Eire	%s	1921 Dec  6 # independence
-			 0:00	GB-Eire	GMT/IST	1940 Feb 25  2:00
-			 0:00	1:00	IST	1946 Oct  6  2:00
-			 0:00	-	GMT	1947 Mar 16  2:00
-			 0:00	1:00	IST	1947 Nov  2  2:00
-			 0:00	-	GMT	1948 Apr 18  2:00
+			 0:00	GB-Eire	GMT/IST	1940 Feb 25  2:00s
+			 0:00	1:00	IST	1946 Oct  6  2:00s
+			 0:00	-	GMT	1947 Mar 16  2:00s
+			 0:00	1:00	IST	1947 Nov  2  2:00s
+			 0:00	-	GMT	1948 Apr 18  2:00s
 			 0:00	GB-Eire	GMT/IST	1968 Oct 27
 			 1:00	-	IST	1971 Oct 31  2:00u
 			 0:00	GB-Eire	GMT/IST	1996
@@ -625,7 +631,7 @@ Rule	Russia	1996	2010	-	Oct	lastSun	 2:00s	0	-
 # Council of Ministers of the USSR from 1989-03-14 No. 227.
 #
 # I did not find full texts of these acts.  For the 1989 one we have
-# title at http://base.garant.ru/70754136/ :
+# title at https://base.garant.ru/70754136/ :
 # "About change in calculation of time on the territories of
 # Lithuanian SSR, Latvian SSR and Estonian SSR, Astrakhan,
 # Kaliningrad, Kirov, Kuybyshev, Ulyanovsk and Uralsk oblasts".
@@ -656,7 +662,7 @@ Rule	Russia	1996	2010	-	Oct	lastSun	 2:00s	0	-
 # http://bmockbe.ru/events/?ID=7583
 #
 # Medvedev signed a law on the calculation of the time (in russian):
-# http://www.regnum.ru/news/polit/1413906.html
+# https://www.regnum.ru/news/polit/1413906.html
 
 # From Arthur David Olson (2011-06-15):
 # Take "abolishing daylight saving time" to mean that time is now considered
@@ -783,7 +789,7 @@ Zone	Europe/Vienna	1:05:21 -	LMT	1893 Apr
 # Sources (Russian language):
 # http://www.belta.by/ru/all_news/society/V-Belarusi-otmenjaetsja-perexod-na-sezonnoe-vremja_i_572952.html
 # http://naviny.by/rubrics/society/2011/09/16/ic_articles_116_175144/
-# http://news.tut.by/society/250578.html
+# https://news.tut.by/society/250578.html
 #
 # From Alexander Bokovoy (2014-10-09):
 # Belarussian government decided against changing to winter time....
@@ -1104,7 +1110,7 @@ Zone America/Thule	-4:35:08 -	LMT	1916 Jul 28 # Pituffik air base
 # for their standard and summer times. He says no, they use "suveaeg"
 # (summer time) and "talveaeg" (winter time).
 
-# From The Baltic Times <http://www.baltictimes.com/> (1999-09-09)
+# From The Baltic Times <https://www.baltictimes.com/> (1999-09-09)
 # via Steffen Thorsen:
 # This year will mark the last time Estonia shifts to summer time,
 # a council of the ruling coalition announced Sept. 6....
@@ -1156,7 +1162,7 @@ Zone	Europe/Tallinn	1:39:00	-	LMT	1880
 # This is documented in Heikki Oja: Aikakirja 2007, published by The Almanac
 # Office of University of Helsinki, ISBN 952-10-3221-9, available online (in
 # Finnish) at
-# http://almanakka.helsinki.fi/aikakirja/Aikakirja2007kokonaan.pdf
+# https://almanakka.helsinki.fi/aikakirja/Aikakirja2007kokonaan.pdf
 #
 # Page 105 (56 in PDF version) has a handy table of all past daylight savings
 # transitions. It is easy enough to interpret without Finnish skills.
@@ -1169,7 +1175,7 @@ Zone	Europe/Tallinn	1:39:00	-	LMT	1880
 
 # From Konstantin Hyppönen (2014-06-13):
 # [Heikki Oja's book Aikakirja 2013]
-# http://almanakka.helsinki.fi/images/aikakirja/Aikakirja2013kokonaan.pdf
+# https://almanakka.helsinki.fi/images/aikakirja/Aikakirja2013kokonaan.pdf
 # pages 104-105, including a scan from a newspaper published on Apr 2 1942
 # say that ... [o]n Apr 2 1942, 24 o'clock (which means Apr 3 1942,
 # 00:00), clocks were moved one hour forward. The newspaper
@@ -1299,7 +1305,7 @@ Zone	Europe/Paris	0:09:21 -	LMT	1891 Mar 15  0:01
 
 # From Jörg Schilling (2002-10-23):
 # In 1945, Berlin was switched to Moscow Summer time (GMT+4) by
-# http://www.dhm.de/lemo/html/biografien/BersarinNikolai/
+# https://www.dhm.de/lemo/html/biografien/BersarinNikolai/
 # General [Nikolai] Bersarin.
 
 # From Paul Eggert (2003-03-08):
@@ -1524,7 +1530,7 @@ Zone Atlantic/Reykjavik	-1:28	-	LMT	1908
 # From Paul Eggert (2016-10-27):
 # Go with INRiM for DST rules, except as corrected by Inglis for 1944
 # for the Kingdom of Italy.  This is consistent with Renzo Baldini.
-# Model Rome's occupation by using using C-Eur rules from 1943-09-10
+# Model Rome's occupation by using C-Eur rules from 1943-09-10
 # to 1944-06-04; although Rome was an open city during this period, it
 # was effectively controlled by Germany.
 #
@@ -1839,14 +1845,14 @@ Zone	Europe/Malta	0:58:04 -	LMT	1893 Nov  2  0:00s # Valletta
 # Following Moldova and neighboring Ukraine- Transnistria (Pridnestrovie)-
 # Tiraspol will go back to winter time on October 30, 2011.
 # News from Moldova (in russian):
-# http://ru.publika.md/link_317061.html
+# https://ru.publika.md/link_317061.html
 
 # From Roman Tudos (2015-07-02):
 # http://lex.justice.md/index.php?action=view&view=doc&lang=1&id=355077
 # From Paul Eggert (2015-07-01):
 # The abovementioned official link to IGO1445-868/2014 states that
 # 2014-10-26's fallback transition occurred at 03:00 local time.  Also,
-# http://www.trm.md/en/social/la-30-martie-vom-trece-la-ora-de-vara
+# https://www.trm.md/en/social/la-30-martie-vom-trece-la-ora-de-vara
 # says the 2014-03-30 spring-forward transition was at 02:00 local time.
 # Guess that since 1997 Moldova has switched one hour before the EU.
 
@@ -1918,7 +1924,7 @@ Zone	Europe/Monaco	0:29:32 -	LMT	1891 Mar 15
 # Amsterdam mean time.
 
 # The data entries before 1945 are taken from
-# http://www.staff.science.uu.nl/~gent0113/wettijd/wettijd.htm
+# https://www.staff.science.uu.nl/~gent0113/wettijd/wettijd.htm
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	Neth	1916	only	-	May	 1	0:00	1:00	NST	# Netherlands Summer Time
@@ -1999,7 +2005,7 @@ Zone	Europe/Oslo	0:43:00 -	LMT	1895 Jan  1
 # so it must have diverged from Oslo time during the war, as Oslo was
 # keeping Berlin time.
 #
-# <http://home.no.net/janmayen/history.htm> says that the meteorologists
+# <https://www.jan-mayen.no/history.htm> says that the meteorologists
 # burned down their station in 1940 and left the island, but returned in
 # 1941 with a small Norwegian garrison and continued operations despite
 # frequent air attacks from Germans.  In 1943 the Americans established a
@@ -2037,7 +2043,7 @@ Rule	Poland	1945	only	-	Apr	29	0:00	1:00	S
 Rule	Poland	1945	only	-	Nov	 1	0:00	0	-
 # For 1946 on the source is Kazimierz Borkowski,
 # Toruń Center for Astronomy, Dept. of Radio Astronomy, Nicolaus Copernicus U.,
-# http://www.astro.uni.torun.pl/~kb/Artykuly/U-PA/Czas2.htm#tth_tAb1
+# https://www.astro.uni.torun.pl/~kb/Artykuly/U-PA/Czas2.htm#tth_tAb1
 # Thanks to Przemysław Augustyniak (2005-05-28) for this reference.
 # He also gives these further references:
 # Mon Pol nr 13, poz 162 (1995) <http://www.abc.com.pl/serwis/mp/1995/0162.htm>
@@ -2071,7 +2077,7 @@ Zone	Europe/Warsaw	1:24:00 -	LMT	1880
 #
 # From Paul Eggert (2014-08-11), after a heads-up from Stephen Colebourne:
 # According to a Portuguese decree (1911-05-26)
-# http://dre.pt/pdf1sdip/1911/05/12500/23132313.pdf
+# https://dre.pt/application/dir/pdf1sdip/1911/05/12500/23132313.pdf
 # Lisbon was at -0:36:44.68, but switched to GMT on 1912-01-01 at 00:00.
 # Round the old offset to -0:36:45.  This agrees with Willett but disagrees
 # with Shanks, who says the transition occurred on 1911-05-24 at 00:00 for
@@ -2253,7 +2259,7 @@ Zone Europe/Bucharest	1:44:24 -	LMT	1891 Oct
 # 2011 No. 725" and contains no other dates or "effective date" information.
 #
 # Another source is
-# http://www.rg.ru/2011/09/06/chas-zona-dok.html
+# https://rg.ru/2011/09/06/chas-zona-dok.html
 # which, according to translate.google.com, begins "Resolution of the
 # Government of the Russian Federation on August 31, 2011 N 725" and also
 # contains "Date first official publication: September 6, 2011 Posted on:
@@ -2261,7 +2267,7 @@ Zone Europe/Bucharest	1:44:24 -	LMT	1891 Oct
 # does not contain any "effective date" information.
 #
 # Another source is
-# http://en.wikipedia.org/wiki/Oymyakonsky_District#cite_note-RuTime-7
+# https://en.wikipedia.org/wiki/Oymyakonsky_District#cite_note-RuTime-7
 # which, in note 8, contains "Resolution No. 725 of August 31, 2011...
 # Effective as of after 7 days following the day of the official publication"
 # but which does not contain any reference to September 6, 2011.
@@ -2297,7 +2303,7 @@ Zone Europe/Bucharest	1:44:24 -	LMT	1891 Oct
 # http://itar-tass.com/obschestvo/1333711
 # http://www.pravo.gov.ru:8080/page.aspx?111660
 # http://www.kremlin.ru/acts/46279
-# From October 26, 2014 the new Russian time zone map will looks like this:
+# From October 26, 2014 the new Russian time zone map will look like this:
 # http://www.worldtimezone.com/dst_news/dst_news_russia-map-2014-07.html
 
 # From Paul Eggert (2006-03-22):
@@ -2344,7 +2350,7 @@ Zone Europe/Bucharest	1:44:24 -	LMT	1891 Oct
 # with maintenance only and represent our best guesses as to which regions
 # are covered by each zone.  They are not meant to be taken as an authoritative
 # listing.  The region codes listed come from
-# http://en.wikipedia.org/w/?title=Federal_subjects_of_Russia&oldid=611810498
+# https://en.wikipedia.org/w/?title=Federal_subjects_of_Russia&oldid=611810498
 # and are used for convenience only; no guarantees are made regarding their
 # future stability.  ISO 3166-2:RU codes are also listed for first-level
 # divisions where available.
@@ -2509,7 +2515,7 @@ Zone Europe/Kaliningrad	 1:22:00 -	LMT	1893 Apr
 # http://www.kaliningradka.ru/site_pc/cherez/index.php?ELEMENT_ID=40091
 # says that Kaliningrad decided not to be an exception 2 days before the
 # 1991-03-31 switch and one person at
-# http://izhevsk.ru/forum_light_message/50/682597-m8369040.html
+# https://izhevsk.ru/forum_light_message/50/682597-m8369040.html
 # says he remembers that Samara opted out of the 1992-01-19 exception
 # 2 days before the switch.
 #
@@ -2581,7 +2587,7 @@ Zone Europe/Simferopol	 2:16:24 -	LMT	1880
 			 3:00	-	MSK	1997 Mar lastSun  1:00u
 # From Alexander Krivenyshev (2014-03-17):
 # time change at 2:00 (2am) on March 30, 2014
-# http://vz.ru/news/2014/3/17/677464.html
+# https://vz.ru/news/2014/3/17/677464.html
 # From Paul Eggert (2014-03-30):
 # Simferopol and Sevastopol reportedly changed their central town clocks
 # late the previous day, but this appears to have been ceremonial
@@ -2764,7 +2770,7 @@ Zone Asia/Omsk		 4:53:30 -	LMT	1919 Nov 14
 # suggests that Altai Republic transitioned to Moscow+3 on
 # 1995-05-28.
 #
-# http://regnum.ru/news/society/1957270.html
+# https://regnum.ru/news/society/1957270.html
 # has some historical data for Altai Krai:
 # before 1957: west part on UTC+6, east on UTC+7
 # after 1957: UTC+7
@@ -3138,8 +3144,8 @@ Zone Asia/Magadan	10:03:12 -	LMT	1924 May  2
 # districts, but have very similar populations.  In fact, Wikipedia currently
 # lists them both as having 3528 people, exactly 1668 males and 1860 females
 # each!  (Yikes!)
-# http://en.wikipedia.org/w/?title=Srednekolymsky_District&oldid=603435276
-# http://en.wikipedia.org/w/?title=Verkhnekolymsky_District&oldid=594378493
+# https://en.wikipedia.org/w/?title=Srednekolymsky_District&oldid=603435276
+# https://en.wikipedia.org/w/?title=Verkhnekolymsky_District&oldid=594378493
 # Assume this is a mistake, albeit an amusing one.
 #
 # Looking at censuses, the populations of the two municipalities seem to have
@@ -3460,7 +3466,7 @@ Zone Europe/Stockholm	1:12:12 -	LMT	1879 Jan  1
 #
 # From Alois Treindl (2013-09-11):
 # The Federal regulations say
-# http://www.admin.ch/opc/de/classified-compilation/20071096/index.html
+# https://www.admin.ch/opc/de/classified-compilation/20071096/index.html
 # ... the meridian for Bern mean time ... is 7 degrees 26' 22.50".
 # Expressed in time, it is 0h29m45.5s.
 
@@ -3537,9 +3543,9 @@ Zone	Europe/Zurich	0:34:08 -	LMT	1853 Jul 16 # See above comment.
 # According to the articles linked below, Turkey will change into summer
 # time zone (GMT+3) on March 28, 2011 at 3:00 a.m. instead of March 27.
 # This change is due to a nationwide exam on 27th.
-# http://www.worldbulletin.net/?aType=haber&ArticleID=70872
+# https://www.worldbulletin.net/?aType=haber&ArticleID=70872
 # Turkish:
-# http://www.hurriyet.com.tr/ekonomi/17230464.asp?gid=373
+# https://www.hurriyet.com.tr/yaz-saati-uygulamasi-bir-gun-ileri-alindi-17230464
 
 # From Faruk Pasin (2014-02-14):
 # The DST for Turkey has been changed for this year because of the
@@ -3675,7 +3681,7 @@ Link	Europe/Istanbul	Asia/Istanbul	# Istanbul is in both continents.
 # http://www.segodnya.ua/news/14290482.html
 #
 # Deputies cancelled the winter time (in Russian)
-# http://www.pravda.com.ua/rus/news/2011/09/20/6600616/
+# https://www.pravda.com.ua/rus/news/2011/09/20/6600616/
 #
 # From Philip Pizzey (2011-10-18):
 # Today my Ukrainian colleagues have informed me that the
diff --git a/contrib/tzdata/leap-seconds.list b/contrib/tzdata/leap-seconds.list
index d0903e7e0ebd..5d5001029667 100644
--- a/contrib/tzdata/leap-seconds.list
+++ b/contrib/tzdata/leap-seconds.list
@@ -199,10 +199,10 @@
 #	current -- the update time stamp, the data and the name of the file
 #	will not change.
 #
-#	Updated through IERS Bulletin C53
-#	File expires on:  28 December 2017
+#	Updated through IERS Bulletin C54
+#	File expires on:  28 June 2018
 #
-#@	3723408000
+#@	3739132800
 #
 2272060800	10	# 1 Jan 1972
 2287785600	11	# 1 Jul 1972
@@ -247,4 +247,4 @@
 #	the hash line is also ignored in the
 #	computation.
 #
-#h	62cf8c5d 8bbb6dcc c61e3b56 c308343 869bb80d
+#h	5101445a 69948b51 9153e2b 2086e3d8 d54561a3
diff --git a/contrib/tzdata/leapseconds b/contrib/tzdata/leapseconds
index 1ebf70fcf61e..a191d5f535a5 100644
--- a/contrib/tzdata/leapseconds
+++ b/contrib/tzdata/leapseconds
@@ -3,19 +3,18 @@
 # This file is in the public domain.
 
 # This file is generated automatically from the data in the public-domain
-# leap-seconds.list file available from most NIST time servers.
-# If the URL <ftp://time.nist.gov/pub/leap-seconds.list> does not work,
-# you should be able to pick up leap-seconds.list from a secondary NIST server.
-# See <http://tf.nist.gov/tf-cgi/servers.cgi> for a list of secondary servers.
+# leap-seconds.list file, which is copied from:
+# ftp://ftp.nist.gov/pub/time/leap-seconds.list
 # For more about leap-seconds.list, please see
 # The NTP Timescale and Leap Seconds
-# http://www.eecis.udel.edu/~mills/leap.html
+# https://www.eecis.udel.edu/~mills/leap.html
 
 # The International Earth Rotation and Reference Systems Service
 # periodically uses leap seconds to keep UTC to within 0.9 s of UT1
 # (which measures the true angular orientation of the earth in space); see
-# Terry J Quinn, The BIPM and the accurate measure of time,
-# Proc IEEE 79, 7 (July 1991), 894-905 <http://dx.doi.org/10.1109/5.84965>.
+# Levine J. Coordinated Universal Time and the leap second.
+# URSI Radio Sci Bull. 2016;89(4):30-6. doi:10.23919/URSIRSB.2016.7909995
+# http://ieeexplore.ieee.org/document/7909995/
 # There were no leap seconds before 1972, because the official mechanism
 # accounting for the discrepancy between atomic time and the earth's rotation
 # did not exist until the early 1970s.
@@ -58,5 +57,5 @@ Leap	2012	Jun	30	23:59:60	+	S
 Leap	2015	Jun	30	23:59:60	+	S
 Leap	2016	Dec	31	23:59:60	+	S
 
-#	Updated through IERS Bulletin C53
-#	File expires on:  28 December 2017
+#	Updated through IERS Bulletin C54
+#	File expires on:  28 June 2018
diff --git a/contrib/tzdata/leapseconds.awk b/contrib/tzdata/leapseconds.awk
index 21fe540791b5..66eb64d3dcab 100644
--- a/contrib/tzdata/leapseconds.awk
+++ b/contrib/tzdata/leapseconds.awk
@@ -8,19 +8,18 @@ BEGIN {
   print "# This file is in the public domain."
   print ""
   print "# This file is generated automatically from the data in the public-domain"
-  print "# leap-seconds.list file available from most NIST time servers."
-  print "# If the URL <ftp://time.nist.gov/pub/leap-seconds.list> does not work,"
-  print "# you should be able to pick up leap-seconds.list from a secondary NIST server."
-  print "# See <http://tf.nist.gov/tf-cgi/servers.cgi> for a list of secondary servers."
+  print "# leap-seconds.list file, which is copied from:"
+  print "# ftp://ftp.nist.gov/pub/time/leap-seconds.list"
   print "# For more about leap-seconds.list, please see"
   print "# The NTP Timescale and Leap Seconds"
-  print "# http://www.eecis.udel.edu/~mills/leap.html"
+  print "# https://www.eecis.udel.edu/~mills/leap.html"
   print ""
   print "# The International Earth Rotation and Reference Systems Service"
   print "# periodically uses leap seconds to keep UTC to within 0.9 s of UT1"
   print "# (which measures the true angular orientation of the earth in space); see"
-  print "# Terry J Quinn, The BIPM and the accurate measure of time,"
-  print "# Proc IEEE 79, 7 (July 1991), 894-905 <http://dx.doi.org/10.1109/5.84965>."
+  print "# Levine J. Coordinated Universal Time and the leap second."
+  print "# URSI Radio Sci Bull. 2016;89(4):30-6. doi:10.23919/URSIRSB.2016.7909995"
+  print "# http://ieeexplore.ieee.org/document/7909995/"
   print "# There were no leap seconds before 1972, because the official mechanism"
   print "# accounting for the discrepancy between atomic time and the earth's rotation"
   print "# did not exist until the early 1970s."
diff --git a/contrib/tzdata/northamerica b/contrib/tzdata/northamerica
index 6ede9dcd96be..e5d3eca41c25 100644
--- a/contrib/tzdata/northamerica
+++ b/contrib/tzdata/northamerica
@@ -105,10 +105,13 @@
 # Last night I heard part of a rebroadcast of a 1945 Arch Oboler radio drama.
 # In the introduction, Oboler spoke of "Eastern Peace Time."
 # An AltaVista search turned up:
-# http://rowayton.org/rhs/hstaug45.html
+# https://web.archive.org/web/20000926032210/http://rowayton.org/rhs/hstaug45.html
 # "When the time is announced over the radio now, it is 'Eastern Peace
 # Time' instead of the old familiar 'Eastern War Time.'  Peace is wonderful."
 # (August 1945) by way of confirmation.
+#
+# From Paul Eggert (2017-09-23):
+# This was the V-J Day issue of the Clamdigger, a Rowayton, CT newsletter.
 
 # From Joseph Gallant citing
 # George H. Douglas, _The Early Days of Radio Broadcasting_ (1987):
@@ -257,7 +260,7 @@ Zone	PST8PDT		 -8:00	US	P%sT
 # HST and HDT are standardized abbreviations for Hawaii-Aleutian
 # standard and daylight times.  See section 9.47 (p 234) of the
 # U.S. Government Printing Office Style Manual (2008)
-# http://www.gpo.gov/fdsys/pkg/GPO-STYLEMANUAL-2008/pdf/GPO-STYLEMANUAL-2008.pdf
+# https://www.gpo.gov/fdsys/pkg/GPO-STYLEMANUAL-2008/pdf/GPO-STYLEMANUAL-2008.pdf
 
 # From Arthur David Olson, 2005-08-09
 # The following was signed into law on 2005-08-08.
@@ -346,7 +349,7 @@ Zone America/New_York	-4:56:02 -	LMT	1883 Nov 18 12:03:58
 # western Tennessee, most of Texas, Wisconsin
 
 # From Larry M. Smith (2006-04-26) re Wisconsin:
-# http://www.legis.state.wi.us/statutes/Stat0175.pdf ...
+# https://docs.legis.wisconsin.gov/statutes/statutes/175.pdf
 # is currently enforced at the 01:00 time of change.  Because the local
 # "bar time" in the state corresponds to 02:00, a number of citations
 # are issued for the "sale of class 'B' alcohol after prohibited
@@ -355,7 +358,7 @@ Zone America/New_York	-4:56:02 -	LMT	1883 Nov 18 12:03:58
 # From Douglas R. Bomberg (2007-03-12):
 # Wisconsin has enacted (nearly eleventh-hour) legislation to get WI
 # Statue 175 closer in synch with the US Congress' intent....
-# http://www.legis.state.wi.us/2007/data/acts/07Act3.pdf
+# https://docs.legis.wisconsin.gov/2007/related/acts/3
 
 # From an email administrator of the City of Fort Pierre, SD (2015-12-21):
 # Fort Pierre is technically located in the Mountain time zone as is
@@ -402,7 +405,7 @@ Zone America/North_Dakota/New_Salem -6:45:39 - LMT	1883 Nov 18 12:14:21
 # ...it appears that Mercer County, North Dakota, changed from the
 # mountain time zone to the central time zone at the last transition from
 # daylight-saving to standard time (on Nov. 7, 2010):
-# http://www.gpo.gov/fdsys/pkg/FR-2010-09-29/html/2010-24376.htm
+# https://www.gpo.gov/fdsys/pkg/FR-2010-09-29/html/2010-24376.htm
 # http://www.bismarcktribune.com/news/local/article_1eb1b588-c758-11df-b472-001cc4c03286.html
 
 # From Andy Lipscomb (2011-01-24):
@@ -453,7 +456,7 @@ Zone America/Denver	-6:59:56 -	LMT	1883 Nov 18 12:00:04
 # legal time, and is not part of the data here.)  See:
 # Ross SA. An energy crisis from the past: Northern California in 1948.
 # Working Paper No. 8, Institute of Governmental Studies, UC Berkeley,
-# 1973-11.  http://escholarship.org/uc/item/8x22k30c
+# 1973-11.  https://escholarship.org/uc/item/8x22k30c
 #
 # In another measure to save electricity, DST was instituted from 1948-03-14
 # at 02:01 to 1949-01-16 at 02:00, with the governor having the option to move
@@ -474,8 +477,8 @@ Zone America/Denver	-6:59:56 -	LMT	1883 Nov 18 12:00:04
 # which established DST from April's last Sunday at 01:00 until September's
 # last Sunday at 02:00. This was amended by 1962's Proposition 6, which changed
 # the fall-back date to October's last Sunday. See:
-# http://repository.uchastings.edu/cgi/viewcontent.cgi?article=1501&context=ca_ballot_props
-# http://repository.uchastings.edu/cgi/viewcontent.cgi?article=1636&context=ca_ballot_props
+# https://repository.uchastings.edu/cgi/viewcontent.cgi?article=1501&context=ca_ballot_props
+# https://repository.uchastings.edu/cgi/viewcontent.cgi?article=1636&context=ca_ballot_props
 #
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER
 Rule	CA	1948	only	-	Mar	14	2:01	1:00	D
@@ -492,20 +495,31 @@ Zone America/Los_Angeles -7:52:58 -	LMT	1883 Nov 18 12:07:02
 # Alaska
 # AK%sT is the modern abbreviation for -09 per USNO.
 #
-# From Paul Eggert (2001-05-30):
+# From Paul Eggert (2017-06-15):
 # Howse writes that Alaska switched from the Julian to the Gregorian calendar,
 # and from east-of-GMT to west-of-GMT days, when the US bought it from Russia.
-# This was on 1867-10-18, a Friday; the previous day was 1867-10-06 Julian,
-# also a Friday.  Include only the time zone part of this transition,
-# ignoring the switch from Julian to Gregorian, since we can't represent
-# the Julian calendar.
-#
-# As far as we know, none of the exact locations mentioned below were
+# On Friday, 1867-10-18 (Gregorian), at precisely 15:30 local time, the
+# Russian forts and fleet at Sitka fired salutes to mark the ceremony of
+# formal transfer.  See the Sacramento Daily Union (1867-11-14), p 3, col 2.
+# https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=SDU18671114.2.12.1
+# Sitka workers did not change their calendars until Sunday, 1867-10-20,
+# and so celebrated two Sundays that week.  See: Ahllund T (tr Hallamaa P).
+# From the memoirs of a Finnish workman. Alaska History. 2006 Fall;21(2):1-25.
+# http://alaskahistoricalsociety.org/wp-content/uploads/2016/12/Ahllund-2006-Memoirs-of-a-Finnish-Workman.pdf
+# Include only the time zone part of this transition, ignoring the switch
+# from Julian to Gregorian, since we can't represent the Julian calendar.
+#
+# As far as we know, of the locations mentioned below only Sitka was
 # permanently inhabited in 1867 by anyone using either calendar.
-# (Yakutat was colonized by the Russians in 1799, but the settlement
-# was destroyed in 1805 by a Yakutat-kon war party.)  However, there
-# were nearby inhabitants in some cases and for our purposes perhaps
-# it's best to simply use the official transition.
+# (Yakutat was colonized by the Russians in 1799, but the settlement was
+# destroyed in 1805 by a Yakutat-kon war party.)  Many of Alaska's inhabitants
+# were unaware of the US acquisition of Alaska, much less of any calendar or
+# time change.  However, the Russian-influenced part of Alaska did observe
+# Russian time, and it is more accurate to model this than to ignore it.
+# The database format requires an exact transition time; use the Russian
+# salute as a somewhat-arbitrary time for the formal transfer of control for
+# all of Alaska.  Sitka's UTC offset is -9:01:13; adjust its 15:30 to the
+# local times of other Alaskan locations so that they change simultaneously.
 
 # From Paul Eggert (2014-07-18):
 # One opinion of the early-1980s turmoil in Alaska over time zones and
@@ -558,10 +572,10 @@ Zone America/Los_Angeles -7:52:58 -	LMT	1883 Nov 18 12:07:02
 # It seems Metlakatla did go off PST on Sunday, November 1, changing
 # their time to AKST and are going to follow Alaska's DST, switching
 # between AKST and AKDT from now on....
-# http://www.krbd.org/2015/10/30/annette-island-times-they-are-a-changing/
+# https://www.krbd.org/2015/10/30/annette-island-times-they-are-a-changing/
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone America/Juneau	 15:02:19 -	LMT	1867 Oct 18
+Zone America/Juneau	 15:02:19 -	LMT	1867 Oct 19 15:33:32
 			 -8:57:41 -	LMT	1900 Aug 20 12:00
 			 -8:00	-	PST	1942
 			 -8:00	US	P%sT	1946
@@ -571,7 +585,7 @@ Zone America/Juneau	 15:02:19 -	LMT	1867 Oct 18
 			 -8:00	US	P%sT	1983 Oct 30  2:00
 			 -9:00	US	Y%sT	1983 Nov 30
 			 -9:00	US	AK%sT
-Zone America/Sitka	 14:58:47 -	LMT	1867 Oct 18
+Zone America/Sitka	 14:58:47 -	LMT	1867 Oct 19 15:30
 			 -9:01:13 -	LMT	1900 Aug 20 12:00
 			 -8:00	-	PST	1942
 			 -8:00	US	P%sT	1946
@@ -579,7 +593,7 @@ Zone America/Sitka	 14:58:47 -	LMT	1867 Oct 18
 			 -8:00	US	P%sT	1983 Oct 30  2:00
 			 -9:00	US	Y%sT	1983 Nov 30
 			 -9:00	US	AK%sT
-Zone America/Metlakatla	 15:13:42 -	LMT	1867 Oct 18
+Zone America/Metlakatla	 15:13:42 -	LMT	1867 Oct 19 15:44:55
 			 -8:46:18 -	LMT	1900 Aug 20 12:00
 			 -8:00	-	PST	1942
 			 -8:00	US	P%sT	1946
@@ -587,14 +601,14 @@ Zone America/Metlakatla	 15:13:42 -	LMT	1867 Oct 18
 			 -8:00	US	P%sT	1983 Oct 30  2:00
 			 -8:00	-	PST	2015 Nov  1  2:00
 			 -9:00	US	AK%sT
-Zone America/Yakutat	 14:41:05 -	LMT	1867 Oct 18
+Zone America/Yakutat	 14:41:05 -	LMT	1867 Oct 19 15:12:18
 			 -9:18:55 -	LMT	1900 Aug 20 12:00
 			 -9:00	-	YST	1942
 			 -9:00	US	Y%sT	1946
 			 -9:00	-	YST	1969
 			 -9:00	US	Y%sT	1983 Nov 30
 			 -9:00	US	AK%sT
-Zone America/Anchorage	 14:00:24 -	LMT	1867 Oct 18
+Zone America/Anchorage	 14:00:24 -	LMT	1867 Oct 19 14:31:37
 			 -9:59:36 -	LMT	1900 Aug 20 12:00
 			-10:00	-	AST	1942
 			-10:00	US	A%sT	1967 Apr
@@ -602,7 +616,7 @@ Zone America/Anchorage	 14:00:24 -	LMT	1867 Oct 18
 			-10:00	US	AH%sT	1983 Oct 30  2:00
 			 -9:00	US	Y%sT	1983 Nov 30
 			 -9:00	US	AK%sT
-Zone America/Nome	 12:58:21 -	LMT	1867 Oct 18
+Zone America/Nome	 12:58:22 -	LMT	1867 Oct 19 13:29:35
 			-11:01:38 -	LMT	1900 Aug 20 12:00
 			-11:00	-	NST	1942
 			-11:00	US	N%sT	1946
@@ -611,7 +625,7 @@ Zone America/Nome	 12:58:21 -	LMT	1867 Oct 18
 			-11:00	US	B%sT	1983 Oct 30  2:00
 			 -9:00	US	Y%sT	1983 Nov 30
 			 -9:00	US	AK%sT
-Zone America/Adak	 12:13:21 -	LMT	1867 Oct 18
+Zone America/Adak	 12:13:22 -	LMT	1867 Oct 19 12:44:35
 			-11:46:38 -	LMT	1900 Aug 20 12:00
 			-11:00	-	NST	1942
 			-11:00	US	N%sT	1946
@@ -647,7 +661,7 @@ Zone America/Adak	 12:13:21 -	LMT	1867 Oct 18
 # "Hawaiian Time" by Robert C. Schmitt and Doak C. Cox appears on pages 207-225
 # of volume 26 of The Hawaiian Journal of History (1992). As of 2010-12-09,
 # the article is available at
-# http://evols.library.manoa.hawaii.edu/bitstream/10524/239/2/JL26215.pdf
+# https://evols.library.manoa.hawaii.edu/bitstream/10524/239/2/JL26215.pdf
 # and indicates that standard time was adopted effective noon, January
 # 13, 1896 (page 218), that in "1933, the Legislature decreed daylight
 # saving for the period between the last Sunday of each April and the
@@ -746,7 +760,7 @@ Zone America/Boise	-7:44:49 -	LMT	1883 Nov 18 12:15:11
 # Indiana
 #
 # For a map of Indiana's time zone regions, see:
-# http://en.wikipedia.org/wiki/Time_in_Indiana
+# https://en.wikipedia.org/wiki/Time_in_Indiana
 #
 # From Paul Eggert (2007-08-17):
 # Since 1970, most of Indiana has been like America/Indiana/Indianapolis,
@@ -973,7 +987,7 @@ Zone America/Kentucky/Louisville -5:43:02 -	LMT	1883 Nov 18 12:16:58
 # From Paul Eggert (2001-07-16):
 # The final rule was published in the
 # Federal Register 65, 160 (2000-08-17), pp 50154-50158.
-# http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2000_register&docid=fr17au00-22
+# https://www.gpo.gov/fdsys/pkg/FR-2000-08-17/html/00-20854.htm
 #
 Zone America/Kentucky/Monticello -5:39:24 - LMT	1883 Nov 18 12:20:36
 			-6:00	US	C%sT	1946
@@ -999,7 +1013,7 @@ Zone America/Kentucky/Monticello -5:39:24 - LMT	1883 Nov 18 12:20:36
 # West Wendover, NV officially switched from Pacific to mountain time on
 # 1999-10-31.  See the
 # Federal Register 64, 203 (1999-10-21), pp 56705-56707.
-# http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=1999_register&docid=fr21oc99-15
+# https://www.gpo.gov/fdsys/pkg/FR-1999-10-21/html/99-27240.htm
 # However, the Federal Register says that West Wendover already operated
 # on mountain time, and the rule merely made this official;
 # hence a separate tz entry is not needed.
@@ -1029,12 +1043,23 @@ Zone America/Kentucky/Monticello -5:39:24 - LMT	1883 Nov 18 12:20:36
 # one hour in 1914."  This change is not in Shanks.  We have no more
 # info, so omit this for now.
 #
+# From Paul Eggert (2017-07-26):
+# Although Shanks says Detroit observed DST in 1967 from 06-14 00:01
+# until 10-29 00:01, I now see multiple reports that this is incorrect.
+# For example, according to a 50-year anniversary report about the 1967
+# Detroit riots and a major-league doubleheader on 1967-07-23, "By the time
+# the last fly ball of the doubleheader settled into the glove of leftfielder
+# Lenny Green, it was after 7 p.m.  Detroit did not observe daylight saving
+# time, so light was already starting to fail.  Twilight was made even deeper
+# by billowing columns of smoke that ascended in an unbroken wall north of the
+# ballpark."  See: Dow B. Detroit '67: As violence unfolded, Tigers played two
+# at home vs. Yankees. Detroit Free Press 2017-07-23.
+# https://www.freep.com/story/sports/mlb/tigers/2017/07/23/detroit-tigers-1967-riot-new-york-yankees/499951001/
+#
 # Most of Michigan observed DST from 1973 on, but was a bit late in 1975.
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER
 Rule	Detroit	1948	only	-	Apr	lastSun	2:00	1:00	D
 Rule	Detroit	1948	only	-	Sep	lastSun	2:00	0	S
-Rule	Detroit	1967	only	-	Jun	14	2:00	1:00	D
-Rule	Detroit	1967	only	-	Oct	lastSun	2:00	0	S
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone America/Detroit	-5:32:11 -	LMT	1905
 			-6:00	-	CST	1915 May 15  2:00
@@ -1098,7 +1123,7 @@ Zone America/Menominee	-5:50:27 -	LMT	1885 Sep 18 12:00
 #	[PDF] (1914-03)
 #
 #	Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94
-#	<http://www.jstor.org/stable/1774359>.
+#	<https://www.jstor.org/stable/1774359>.
 #
 # See the 'europe' file for Greenland.
 
@@ -1144,19 +1169,19 @@ Zone America/Menominee	-5:50:27 -	LMT	1885 Sep 18 12:00
 # The British Columbia government announced yesterday that it will
 # adjust daylight savings next year to align with changes in the
 # U.S. and the rest of Canada....
-# http://www2.news.gov.bc.ca/news_releases_2005-2009/2006AG0014-000330.htm
+# https://archive.news.gov.bc.ca/releases/news_releases_2005-2009/2006AG0014-000330.htm
 # ...
 # Nova Scotia
 # Daylight saving time will be extended by four weeks starting in 2007....
-# http://www.gov.ns.ca/just/regulations/rg2/2006/ma1206.pdf
+# https://www.novascotia.ca/just/regulations/rg2/2006/ma1206.pdf
 #
 # [For New Brunswick] the new legislation dictates that the time change is to
 # be done at 02:00 instead of 00:01.
-# http://www.gnb.ca/0062/acts/BBA-2006/Chap-19.pdf
+# https://www.gnb.ca/0062/acts/BBA-2006/Chap-19.pdf
 # ...
 # Manitoba has traditionally changed the clock every fall at 03:00.
 # As of 2006, the transition is to take place one hour earlier at 02:00.
-# http://web2.gov.mb.ca/laws/statutes/ccsm/o030e.php
+# https://web2.gov.mb.ca/laws/statutes/ccsm/o030e.php
 # ...
 # [Alberta, Ontario, Quebec] will follow US rules.
 # http://www.qp.gov.ab.ca/documents/spring/CH03_06.CFM
@@ -1170,7 +1195,7 @@ Zone America/Menominee	-5:50:27 -	LMT	1885 Sep 18 12:00
 # http://www.hoa.gov.nl.ca/hoa/bills/Bill0634.htm
 # ...
 # Yukon
-# http://www.gov.yk.ca/legislation/regs/oic2006_127.pdf
+# https://www.gov.yk.ca/legislation/regs/oic2006_127.pdf
 # ...
 # N.W.T. will follow US rules.  Whoever maintains the government web site
 # does not seem to believe in bookmarks.  To see the news release, click the
@@ -1191,8 +1216,8 @@ Zone America/Menominee	-5:50:27 -	LMT	1885 Sep 18 12:00
 # time and daylight saving time arrangements in Canada circa 1998.
 #
 # National Research Council Canada maintains info about time zones and DST.
-# http://www.nrc-cnrc.gc.ca/eng/services/time/time_zones.html
-# http://www.nrc-cnrc.gc.ca/eng/services/time/faq/index.html#Q5
+# https://www.nrc-cnrc.gc.ca/eng/services/time/time_zones.html
+# https://www.nrc-cnrc.gc.ca/eng/services/time/faq/index.html#Q5
 # Its unofficial information is often taken from Matthews and Vincent.
 
 # From Paul Eggert (2006-06-27):
@@ -1229,11 +1254,13 @@ Rule	Canada	2007	max	-	Nov	Sun>=1	2:00	0	S
 
 # Newfoundland and Labrador
 
-# From Paul Eggert (2000-10-02):
-# Matthews and Vincent (1998) write that Labrador should use NST/NDT,
-# but the only part of Labrador that follows the rules is the
-# southeast corner, including Port Hope Simpson and Mary's Harbour,
-# but excluding, say, Black Tickle.
+# From Paul Eggert (2017-10-14):
+# Legally Labrador should observe Newfoundland time; see:
+# McLeod J. Labrador time - legal or not? St. John's Telegram, 2017-10-07
+# http://www.thetelegram.com/news/local/labrador-time--legal-or-not-154860/
+# Matthews and Vincent (1998) write that the only part of Labrador
+# that follows the rules is the southeast corner, including Port Hope
+# Simpson and Mary's Harbour, but excluding, say, Black Tickle.
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	StJohns	1917	only	-	Apr	 8	2:00	1:00	D
@@ -1433,7 +1460,7 @@ Zone America/Moncton	-4:19:08 -	LMT	1883 Dec  9
 # http://www.justice.gouv.qc.ca/english/publications/generale/temps-minganie-a.htm
 # that the coastal strip from just east of Natashquan to Blanc-Sablon
 # observes Atlantic standard time all year round.
-# http://www.assnat.qc.ca/Media/Process.aspx?MediaId=ANQ.Vigie.Bll.DocumentGenerique_8845en
+# https://www.assnat.qc.ca/Media/Process.aspx?MediaId=ANQ.Vigie.Bll.DocumentGenerique_8845en
 # says this common practice was codified into law as of 2007.
 # For lack of better info, guess this practice began around 1970, contra to
 # Shanks & Pottenger who have this region observing AST/ADT.
@@ -1465,6 +1492,11 @@ Zone America/Blanc-Sablon -3:48:28 -	LMT	1884
 # earlier in June).
 #
 # Kenora, Ontario, was to abandon DST on 1914-06-01 (-05-21).
+#
+# From Paul Eggert (2017-07-08):
+# For more on Orillia, see: Daubs K. Bold attempt at daylight saving
+# time became a comic failure in Orillia. Toronto Star 2017-07-08.
+# https://www.thestar.com/news/insight/2017/07/08/bold-attempt-at-daylight-saving-time-became-a-comic-failure-in-orillia.html
 
 # From Paul Eggert (1997-10-17):
 # Mark Brader writes that an article in the 1997-10-14 Toronto Star
@@ -1956,7 +1988,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 #	* 1967. Paragraph 28(34)(g) of the Interpretation Act, S.C. 1967-68,
 #	c. 7 defines Yukon standard time as UTC-9....
 #	see Interpretation Act, R.S.C. 1985, c. I-21, s. 35(1).
-#	[http://canlii.ca/t/7vhg]
+#	[https://www.canlii.org/en/ca/laws/stat/rsc-1985-c-i-21/latest/rsc-1985-c-i-21.html]
 #	* C.O. 1973/214 switched Yukon to PST on 1973-10-28 00:00.
 #	* O.I.C. 1980/02 established DST.
 #	* O.I.C. 1987/056 changed DST to Apr firstSun 2:00 to Oct lastSun 2:00.
@@ -2021,7 +2053,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 #     hours behind Greenwich Time.
 #
 # * Yukon Standard Time defined as Pacific Standard Time, YCO 1973/214
-#   http://www.canlii.org/en/yk/laws/regu/yco-1973-214/latest/yco-1973-214.html
+#   https://www.canlii.org/en/yk/laws/regu/yco-1973-214/latest/yco-1973-214.html
 #   C.O. 1973/214 INTERPRETATION ACT ...
 #
 #     1. Effective October 28, 1973 Commissioner's Order 1967/59 is hereby
@@ -2036,7 +2068,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 #   http://? - no online source found
 #
 # * Yukon Daylight Saving Time, YOIC 1987/56
-#   http://www.canlii.org/en/yk/laws/regu/yoic-1987-56/latest/yoic-1987-56.html
+#   https://www.canlii.org/en/yk/laws/regu/yoic-1987-56/latest/yoic-1987-56.html
 #   O.I.C. 1987/056 INTERPRETATION ACT ...
 #
 #   In every year between
@@ -2048,7 +2080,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 #   Dated ... 9th day of March, A.D., 1987.
 #
 # * Yukon Daylight Saving Time 2006, YOIC 2006/127
-#   http://www.canlii.org/en/yk/laws/regu/yoic-2006-127/latest/yoic-2006-127.html
+#   https://www.canlii.org/en/yk/laws/regu/yoic-2006-127/latest/yoic-2006-127.html
 #   O.I.C. 2006/127 INTERPRETATION ACT ...
 #
 #     1. In Yukon each year the time for general purposes shall be 7 hours
@@ -2062,7 +2094,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 #     3. This order comes into force January 1, 2007.
 #
 # * Interpretation Act, RSY 2002, c 125
-# http://www.canlii.org/en/yk/laws/stat/rsy-2002-c-125/latest/rsy-2002-c-125.html
+# https://www.canlii.org/en/yk/laws/stat/rsy-2002-c-125/latest/rsy-2002-c-125.html
 
 # From Rives McDow (1999-09-04):
 # Nunavut ... moved ... to incorporate the whole territory into one time zone.
@@ -2105,7 +2137,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 
 # From Michaela Rodrigue, writing in the
 # Nunatsiaq News (1999-11-19):
-# http://www.nunatsiaq.com/archives/nunavut991130/nvt91119_17.html
+# http://www.nunatsiaqonline.ca/archives/nunavut991130/nvt91119_17.html
 # Clyde River, Pangnirtung and Sanikiluaq now operate with two time zones,
 # central - or Nunavut time - for government offices, and eastern time
 # for municipal offices and schools....  Igloolik [was similar but then]
@@ -2123,7 +2155,7 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 # Central Time and Southampton Island [in the Central zone] is not
 # required to use daylight savings.
 
-# From <http://www.nunatsiaq.com/archives/nunavut001130/nvt21110_02.html>
+# From <http://www.nunatsiaqonline.ca/archives/nunavut001130/nvt21110_02.html>
 # Nunavut now has two time zones (2000-11-10):
 # The Nunavut government would allow its employees in Kugluktuk and
 # Cambridge Bay to operate on central time year-round, putting them
@@ -2454,7 +2486,7 @@ Zone America/Dawson	-9:17:40 -	LMT	1900 Aug 20
 # http://gaceta.diputados.gob.mx/Gaceta/61/2009/dic/V2-101209.html
 #
 # Our page:
-# http://www.timeanddate.com/news/time/north-mexico-dst-change.html
+# https://www.timeanddate.com/news/time/north-mexico-dst-change.html
 
 # From Arthur David Olson (2010-01-20):
 # The page
@@ -2873,7 +2905,7 @@ Zone America/Costa_Rica	-5:36:13 -	LMT	1890        # San José
 # http://www.nnc.cubaweb.cu/marzo-2008/cien-1-11-3-08.htm
 #
 # Some more background information is posted here:
-# http://www.timeanddate.com/news/time/cuba-starts-dst-march-16.html
+# https://www.timeanddate.com/news/time/cuba-starts-dst-march-16.html
 #
 # The article also says that Cuba has been observing DST since 1963,
 # while Shanks (and tzdata) has 1965 as the first date (except in the
@@ -2920,7 +2952,7 @@ Zone America/Costa_Rica	-5:36:13 -	LMT	1890        # San José
 # http://granma.co.cu/2011/03/08/nacional/artic01.html
 #
 # Our info:
-# http://www.timeanddate.com/news/time/cuba-starts-dst-2011.html
+# https://www.timeanddate.com/news/time/cuba-starts-dst-2011.html
 #
 # From Steffen Thorsen (2011-10-30)
 # Cuba will end DST two weeks later this year. Instead of going back
@@ -2930,7 +2962,7 @@ Zone America/Costa_Rica	-5:36:13 -	LMT	1890        # San José
 # http://www.radioangulo.cu/noticias/cuba/17105-cuba-restablecera-el-horario-del-meridiano-de-greenwich.html
 #
 # Our page:
-# http://www.timeanddate.com/news/time/cuba-time-changes-2011.html
+# https://www.timeanddate.com/news/time/cuba-time-changes-2011.html
 #
 # From Steffen Thorsen (2012-03-01)
 # According to Radio Reloj, Cuba will start DST on Midnight between March
@@ -2940,7 +2972,7 @@ Zone America/Costa_Rica	-5:36:13 -	LMT	1890        # San José
 # http://www.radioreloj.cu/index.php/noticias-radio-reloj/71-miscelaneas/7529-cuba-aplicara-el-horario-de-verano-desde-el-1-de-abril
 #
 # Our info on it:
-# http://www.timeanddate.com/news/time/cuba-starts-dst-2012.html
+# https://www.timeanddate.com/news/time/cuba-starts-dst-2012.html
 
 # From Steffen Thorsen (2012-11-03):
 # Radio Reloj and many other sources report that Cuba is changing back
@@ -3135,8 +3167,8 @@ Zone America/Guatemala	-6:02:04 -	LMT	1918 Oct 5
 # From Steffen Thorsen (2016-03-12):
 # Jean Antoine, editor of www.haiti-reference.com informed us that Haiti
 # are not going on DST this year.  Several other resources confirm this: ...
-# http://www.radiotelevisioncaraibes.com/presse/heure_d_t_pas_de_changement_d_heure_pr_vu_pour_cet_ann_e.html
-# http://www.vantbefinfo.com/changement-dheure-pas-pour-haiti/
+# https://www.radiotelevisioncaraibes.com/presse/heure_d_t_pas_de_changement_d_heure_pr_vu_pour_cet_ann_e.html
+# https://www.vantbefinfo.com/changement-dheure-pas-pour-haiti/
 # http://news.anmwe.com/haiti-lheure-nationale-ne-sera-ni-avancee-ni-reculee-cette-annee/
 
 # From Steffen Thorsen (2017-03-12):
@@ -3335,7 +3367,7 @@ Zone America/Miquelon	-3:44:40 -	LMT	1911 May 15 # St Pierre
 # Turks and Caicos
 #
 # From Chris Dunn in
-# http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=415007
+# https://bugs.debian.org/415007
 # (2007-03-15): In the Turks & Caicos Islands (America/Grand_Turk) the
 # daylight saving dates for time changes have been adjusted to match
 # the recent U.S. change of dates.
@@ -3357,12 +3389,25 @@ Zone America/Miquelon	-3:44:40 -	LMT	1911 May 15 # St Pierre
 # "permanent daylight saving time" by one year....
 # http://tcweeklynews.com/time-change-to-go-ahead-this-november-p5437-127.htm
 #
+# From the Turks & Caicos Cabinet (2017-07-20), heads-up from Steffen Thorsen:
+# ... agreed to the reintroduction in TCI of Daylight Saving Time (DST)
+# during the summer months and Standard Time, also known as Local
+# Time, during the winter months with effect from April 2018 ...
+# https://www.gov.uk/government/news/turks-and-caicos-post-cabinet-meeting-statement--3
+#
+# From Paul Eggert (2017-08-26):
+# The date of effect of the spring 2018 change appears to be March 11,
+# which makes more sense.  See: Hamilton D. Time change back
+# by March 2018 for TCI. Magnetic Media. 2017-08-25.
+# http://magneticmediatv.com/2017/08/time-change-back-by-march-2018-for-tci/
+#
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone America/Grand_Turk	-4:44:32 -	LMT	1890
 			-5:07:11 -	KMT	1912 Feb # Kingston Mean Time
 			-5:00	-	EST	1979
 			-5:00	US	E%sT	2015 Nov Sun>=1 2:00
-			-4:00	-	AST
+			-4:00	-	AST	2018 Mar 11 3:00
+			-5:00	US	E%sT
 
 # British Virgin Is
 # Virgin Is
diff --git a/contrib/tzdata/southamerica b/contrib/tzdata/southamerica
index 6038c3b65c26..bbae2261560b 100644
--- a/contrib/tzdata/southamerica
+++ b/contrib/tzdata/southamerica
@@ -22,7 +22,7 @@
 #
 # For data circa 1899, a common source is:
 # Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94.
-# http://www.jstor.org/stable/1774359
+# https://www.jstor.org/stable/1774359
 #
 # These tables use numeric abbreviations like -03 and -0330 for
 # integer hour and minute UTC offsets.  Although earlier editions used
@@ -265,8 +265,8 @@ Rule	Arg	2008	only	-	Oct	Sun>=15	0:00	1:00	S
 #
 # Es inminente que en San Luis atrasen una hora los relojes
 # (It is imminent in San Luis clocks one hour delay)
-# http://www.lagaceta.com.ar/nota/253414/Economia/Es-inminente-que-en-San-Luis-atrasen-una-hora-los-relojes.html
-# http://www.worldtimezone.net/dst_news/dst_news_argentina02.html
+# https://www.lagaceta.com.ar/nota/253414/Economia/Es-inminente-que-en-San-Luis-atrasen-una-hora-los-relojes.html
+# http://www.worldtimezone.com/dst_news/dst_news_argentina02.html
 
 # From Jesper Nørgaard Welen (2008-01-18):
 # The page of the San Luis provincial government
@@ -385,7 +385,7 @@ Rule	Arg	2008	only	-	Oct	Sun>=15	0:00	1:00	S
 # Perhaps San Luis operates on the legal fiction that it is at -04
 # with perpetual summer time, but ordinary usage typically seems to
 # just say it's at -03; see, for example,
-# http://es.wikipedia.org/wiki/Hora_oficial_argentina
+# https://es.wikipedia.org/wiki/Hora_oficial_argentina
 # We've documented similar situations as being plain changes to
 # standard time, so let's do that here too.  This does not change UTC
 # offsets, only tm_isdst and the time zone abbreviations.  One minor
@@ -716,7 +716,7 @@ Zone	America/La_Paz	-4:32:36 -	LMT	1890
 # (Portuguese)
 #
 # We have a written a short article about it as well:
-# http://www.timeanddate.com/news/time/brazil-dst-2008-2009.html
+# https://www.timeanddate.com/news/time/brazil-dst-2008-2009.html
 #
 # From Alexander Krivenyshev (2011-10-04):
 # State Bahia will return to Daylight savings time this year after 8 years off.
@@ -725,7 +725,7 @@ Zone	America/La_Paz	-4:32:36 -	LMT	1890
 
 # In Portuguese:
 # http://g1.globo.com/bahia/noticia/2011/10/governador-jaques-wagner-confirma-horario-de-verao-na-bahia.html
-# http://noticias.terra.com.br/brasil/noticias/0,,OI5390887-EI8139,00-Bahia+volta+a+ter+horario+de+verao+apos+oito+anos.html
+# https://noticias.terra.com.br/brasil/noticias/0,,OI5390887-EI8139,00-Bahia+volta+a+ter+horario+de+verao+apos+oito+anos.html
 
 # From Guilherme Bernardes Rodrigues (2011-10-07):
 # There is news in the media, however there is still no decree about it.
@@ -751,16 +751,16 @@ Zone	America/La_Paz	-4:32:36 -	LMT	1890
 
 # From Rodrigo Severo (2012-10-16):
 # Tocantins state will have DST.
-# http://noticias.terra.com.br/brasil/noticias/0,,OI6232536-EI306.html
+# https://noticias.terra.com.br/brasil/noticias/0,,OI6232536-EI306.html
 
 # From Steffen Thorsen (2013-09-20):
 # Tocantins in Brazil is very likely not to observe DST from October....
 # http://conexaoto.com.br/2013/09/18/ministerio-confirma-que-tocantins-esta-fora-do-horario-de-verao-em-2013-mas-falta-publicacao-de-decreto
 # We will keep this article updated when this is confirmed:
-# http://www.timeanddate.com/news/time/brazil-starts-dst-2013.html
+# https://www.timeanddate.com/news/time/brazil-starts-dst-2013.html
 
 # From Steffen Thorsen (2013-10-17):
-# http://www.timeanddate.com/news/time/acre-amazonas-change-time-zone.html
+# https://www.timeanddate.com/news/time/acre-amazonas-change-time-zone.html
 # Senator Jorge Viana announced that Acre will change time zone on November 10.
 # He did not specify the time of the change, nor if western parts of Amazonas
 # will change as well.
@@ -1076,18 +1076,18 @@ Zone America/Rio_Branco	-4:31:12 -	LMT	1914
 # the following source, cited by Oscar van Vlijmen (2006-10-08):
 # [1] Chile Law
 # http://www.webexhibits.org/daylightsaving/chile.html
-# This contains a copy of a this official table:
+# This contains a copy of this official table:
 # Cambios en la hora oficial de Chile desde 1900 (retrieved 2008-03-30)
-# http://web.archive.org/web/20080330200901/http://www.horaoficial.cl/cambio.htm
+# https://web.archive.org/web/20080330200901/http://www.horaoficial.cl/cambio.htm
 # [1] needs several corrections, though.
 #
 # The first set of corrections is from:
 # [2] History of the Official Time of Chile
 # http://www.horaoficial.cl/ing/horaof_ing.html (retrieved 2012-03-06).  See:
-# http://web.archive.org/web/20120306042032/http://www.horaoficial.cl/ing/horaof_ing.html
+# https://web.archive.org/web/20120306042032/http://www.horaoficial.cl/ing/horaof_ing.html
 # This is an English translation of:
 # Historia de la hora oficial de Chile (retrieved 2012-10-24).  See:
-# http://web.archive.org/web/20121024234627/http://www.horaoficial.cl/horaof.htm
+# https://web.archive.org/web/20121024234627/http://www.horaoficial.cl/horaof.htm
 # A fancier Spanish version (requiring mouse-clicking) is at:
 # http://www.horaoficial.cl/historia_hora.html
 # Conflicts between [1] and [2] were resolved as follows:
@@ -1363,10 +1363,10 @@ Link	America/Curacao	America/Kralendijk	# Caribbean Netherlands
 # Milne says the Central and South American Telegraph Company used -5:24:15.
 #
 # From Alois Treindl (2016-12-15):
-# http://www.elcomercio.com/actualidad/hora-sixto-1993.html
+# https://www.elcomercio.com/actualidad/hora-sixto-1993.html
 # ... Whether the law applied also to Galápagos, I do not know.
 # From Paul Eggert (2016-12-15):
-# http://www.elcomercio.com/afull/modificacion-husohorario-ecuador-presidentes-decreto.html
+# https://www.elcomercio.com/afull/modificacion-husohorario-ecuador-presidentes-decreto.html
 # This says President Sixto Durán Ballén signed decree No. 285, which
 # established DST from 1992-11-28 to 1993-02-05; it does not give transition
 # times.  The people called it "hora de Sixto" ("Sixto hour").  The change did
@@ -1778,7 +1778,7 @@ Zone America/Montevideo	-3:44:44 -	LMT	1898 Jun 28
 # hours of presidential broadcasts, hours of lines,' quipped comedian
 # Jean Mary Curró ...". See: Cawthorne A, Kai D. Venezuela scraps
 # half-hour time difference set by Chavez. Reuters 2016-04-15 14:50 -0400
-# http://www.reuters.com/article/us-venezuela-timezone-idUSKCN0XC2BE
+# https://www.reuters.com/article/us-venezuela-timezone-idUSKCN0XC2BE
 #
 # From Matt Johnson (2016-04-20):
 # ... published in the official Gazette [2016-04-18], here:
diff --git a/contrib/tzdata/theory.html b/contrib/tzdata/theory.html
new file mode 100644
index 000000000000..965135d7e541
--- /dev/null
+++ b/contrib/tzdata/theory.html
@@ -0,0 +1,1034 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <title>Theory and pragmatics of the tz code and data</title>
+  <meta charset="UTF-8">
+</head>
+
+<!-- The somewhat-unusal indenting style in this file is intended to
+     shrink the output of the shell command 'diff Theory Theory.html',
+     where 'Theory' was the plain text file that this file is derived
+     from.  The 'Theory' file used leading white space to indent, and
+     when possible that indentation is preserved here.  Eventually we
+     may stop doing this and remove this comment.  -->
+
+<body>
+  <h1>Theory and pragmatics of the tz code and data</h1>
+  <h3>Outline</h3>
+  <nav>
+    <ul>
+      <li><a href="#scope">Scope of the tz database</a></li>
+      <li><a href="#naming">Names of time zone rules</a></li>
+      <li><a href="#abbreviations">Time zone abbreviations</a></li>
+      <li><a href="#accuracy">Accuracy of the tz database</a></li>
+      <li><a href="#functions">Time and date functions</a></li>
+      <li><a href="#stability">Interface stability</a></li>
+      <li><a href="#calendar">Calendrical issues</a></li>
+      <li><a href="#planets">Time and time zones on other planets</a></li>
+    </ul>
+  </nav>
+
+
+  <section>
+    <h2 id="scope">Scope of the tz database</h2>
+<p>
+The tz database attempts to record the history and predicted future of
+all computer-based clocks that track civil time.  To represent this
+data, the world is partitioned into regions whose clocks all agree
+about timestamps that occur after the somewhat-arbitrary cutoff point
+of the POSIX Epoch (1970-01-01 00:00:00 UTC).  For each such region,
+the database records all known clock transitions, and labels the region
+with a notable location.  Although 1970 is a somewhat-arbitrary
+cutoff, there are significant challenges to moving the cutoff earlier
+even by a decade or two, due to the wide variety of local practices
+before computer timekeeping became prevalent.
+</p>
+
+<p>
+Clock transitions before 1970 are recorded for each such location,
+because most systems support timestamps before 1970 and could
+misbehave if data entries were omitted for pre-1970 transitions.
+However, the database is not designed for and does not suffice for
+applications requiring accurate handling of all past times everywhere,
+as it would take far too much effort and guesswork to record all
+details of pre-1970 civil timekeeping.
+</p>
+
+<p>
+As described below, reference source code for using the tz database is
+also available.  The tz code is upwards compatible with POSIX, an
+international standard for UNIX-like systems.  As of this writing, the
+current edition of POSIX is:
+  <a href="http://pubs.opengroup.org/onlinepubs/9699919799/">
+  The Open Group Base Specifications Issue 7</a>,
+  IEEE Std 1003.1-2008, 2016 Edition.
+</p>
+  </section>
+
+
+
+  <section>
+    <h2 id="naming">Names of time zone rules</h2>
+<p>
+Each of the database's time zone rules has a unique name.
+Inexperienced users are not expected to select these names unaided.
+Distributors should provide documentation and/or a simple selection
+interface that explains the names; for one example, see the 'tzselect'
+program in the tz code.  The
+<a href="http://cldr.unicode.org/">Unicode Common Locale Data
+Repository</a> contains data that may be useful for other
+selection interfaces.
+</p>
+
+<p>
+The time zone rule naming conventions attempt to strike a balance
+among the following goals:
+</p>
+<ul>
+  <li>
+   Uniquely identify every region where clocks have agreed since 1970.
+   This is essential for the intended use: static clocks keeping local
+   civil time.
+  </li>
+  <li>
+   Indicate to experts where that region is.
+  </li>
+  <li>
+   Be robust in the presence of political changes.  For example, names
+   of countries are ordinarily not used, to avoid incompatibilities
+   when countries change their name (e.g. Zaire&rarr;Congo) or when
+   locations change countries (e.g. Hong Kong from UK colony to
+   China).
+  </li>
+  <li>
+   Be portable to a wide variety of implementations.
+  </li>
+  <li>
+   Use a consistent naming conventions over the entire world.
+  </li>
+</ul>
+<p>
+Names normally have the
+form <var>AREA</var><code>/</code><var>LOCATION</var>,
+where <var>AREA</var> is the name of a continent or ocean,
+and <var>LOCATION</var> is the name of a specific
+location within that region.  North and South America share the same
+area, '<code>America</code>'.  Typical names are
+'<code>Africa/Cairo</code>', '<code>America/New_York</code>', and
+'<code>Pacific/Honolulu</code>'.
+</p>
+
+<p>
+Here are the general rules used for choosing location names,
+in decreasing order of importance:
+</p>
+<ul>
+  <li>
+	Use only valid POSIX file name components (i.e., the parts of
+		names other than '<code>/</code>').  Do not use the file name
+		components '<code>.</code>' and '<code>..</code>'.
+		Within a file name component,
+		use only ASCII letters, '<code>.</code>',
+		'<code>-</code>' and '<code>_</code>'.  Do not use
+		digits, as that might create an ambiguity with POSIX
+		TZ strings.  A file name component must not exceed 14
+		characters or start with '<code>-</code>'.  E.g.,
+		prefer '<code>Brunei</code>' to
+		'<code>Bandar_Seri_Begawan</code>'.  Exceptions: see
+		the discussion
+		of legacy names below.
+  </li>
+  <li>
+	A name must not be empty, or contain '<code>//</code>', or
+	start or end with '<code>/</code>'.
+  </li>
+  <li>
+	Do not use names that differ only in case.  Although the reference
+		implementation is case-sensitive, some other implementations
+		are not, and they would mishandle names differing only in case.
+  </li>
+  <li>
+	If one name <var>A</var> is an initial prefix of another
+		name <var>AB</var> (ignoring case), then <var>B</var>
+		must not start with '<code>/</code>', as a
+		regular file cannot have
+		the same name as a directory in POSIX.  For example,
+		'<code>America/New_York</code>' precludes
+		'<code>America/New_York/Bronx</code>'.
+  </li>
+  <li>
+	Uninhabited regions like the North Pole and Bouvet Island
+		do not need locations, since local time is not defined there.
+  </li>
+  <li>
+	There should typically be at least one name for each ISO 3166-1
+		officially assigned two-letter code for an inhabited country
+		or territory.
+  </li>
+  <li>
+	If all the clocks in a region have agreed since 1970,
+		don't bother to include more than one location
+		even if subregions' clocks disagreed before 1970.
+		Otherwise these tables would become annoyingly large.
+  </li>
+  <li>
+	If a name is ambiguous, use a less ambiguous alternative;
+		e.g. many cities are named San José and Georgetown, so
+		prefer '<code>Costa_Rica</code>' to '<code>San_Jose</code>' and '<code>Guyana</code>' to '<code>Georgetown</code>'.
+  </li>
+  <li>
+	Keep locations compact.  Use cities or small islands, not countries
+		or regions, so that any future time zone changes do not split
+		locations into different time zones.  E.g. prefer
+		'<code>Paris</code>' to '<code>France</code>', since
+		France has had multiple time zones.
+  </li>
+  <li>
+	Use mainstream English spelling, e.g. prefer
+		'<code>Rome</code>' to '<code>Roma</code>', and prefer
+		'<code>Athens</code>' to the Greek
+		'<code>Αθήνα</code>' or the Romanized
+		'<code>Athína</code>'.
+		The POSIX file name restrictions encourage this rule.
+  </li>
+  <li>
+	Use the most populous among locations in a zone,
+		e.g. prefer '<code>Shanghai</code>' to
+		'<code>Beijing</code>'.  Among locations with
+		similar populations, pick the best-known location,
+		e.g. prefer '<code>Rome</code>' to '<code>Milan</code>'.
+  </li>
+  <li>
+	Use the singular form, e.g. prefer '<code>Canary</code>' to '<code>Canaries</code>'.
+  </li>
+  <li>
+	Omit common suffixes like '<code>_Islands</code>' and
+		'<code>_City</code>', unless that would lead to
+		ambiguity.  E.g. prefer '<code>Cayman</code>' to
+		'<code>Cayman_Islands</code>' and
+		'<code>Guatemala</code>' to
+		'<code>Guatemala_City</code>', but prefer
+		'<code>Mexico_City</code>' to '<code>Mexico</code>'
+		because the country
+		of Mexico has several time zones.
+  </li>
+  <li>
+	Use '<code>_</code>' to represent a space.
+  </li>
+  <li>
+	Omit '<code>.</code>' from abbreviations in names, e.g. prefer
+		'<code>St_Helena</code>' to '<code>St._Helena</code>'.
+  </li>
+  <li>
+	Do not change established names if they only marginally
+		violate the above rules.  For example, don't change
+		the existing name '<code>Rome</code>' to
+		'<code>Milan</code>' merely because
+		Milan's population has grown to be somewhat greater
+		than Rome's.
+  </li>
+  <li>
+	If a name is changed, put its old spelling in the
+		'<code>backward</code>' file.
+		This means old spellings will continue to work.
+  </li>
+</ul>
+
+<p>
+The file '<code>zone1970.tab</code>' lists geographical locations used
+to name time
+zone rules.  It is intended to be an exhaustive list of names for
+geographic regions as described above; this is a subset of the names
+in the data.  Although a '<code>zone1970.tab</code>' location's longitude
+corresponds to its LMT offset with one hour for every 15 degrees east
+longitude, this relationship is not exact.
+</p>
+
+<p>
+Older versions of this package used a different naming scheme,
+and these older names are still supported.
+See the file '<code>backward</code>' for most of these older names
+(e.g., '<code>US/Eastern</code>' instead of '<code>America/New_York</code>').
+The other old-fashioned names still supported are
+'<code>WET</code>', '<code>CET</code>', '<code>MET</code>', and '<code>EET</code>' (see the file '<code>europe</code>').
+</p>
+
+<p>
+Older versions of this package defined legacy names that are
+incompatible with the first rule of location names, but which are
+still supported.  These legacy names are mostly defined in the file
+'<code>etcetera</code>'.  Also, the file '<code>backward</code>' defines the legacy names
+'<code>GMT0</code>', '<code>GMT-0</code>' and '<code>GMT+0</code>', and the file '<code>northamerica</code>' defines the
+legacy names '<code>EST5EDT</code>', '<code>CST6CDT</code>', '<code>MST7MDT</code>', and '<code>PST8PDT</code>'.
+</p>
+
+<p>
+Excluding '<code>backward</code>' should not affect the other data.  If
+'<code>backward</code>' is excluded, excluding '<code>etcetera</code>' should not affect the
+remaining data.
+</p>
+
+
+  </section>
+  <section>
+    <h2 id="abbreviations">Time zone abbreviations</h2>
+<p>
+When this package is installed, it generates time zone abbreviations
+like '<code>EST</code>' to be compatible with human tradition and POSIX.
+Here are the general rules used for choosing time zone abbreviations,
+in decreasing order of importance:
+<ul>
+  <li>
+	Use three or more characters that are ASCII alphanumerics or
+		'<code>+</code>' or '<code>-</code>'.
+		Previous editions of this database also used characters like
+		'<code> </code>' and '<code>?</code>', but these
+		characters have a special meaning to
+		the shell and cause commands like
+			'<code>set `date`</code>'
+		to have unexpected effects.
+		Previous editions of this rule required upper-case letters,
+		but the Congressman who introduced Chamorro Standard Time
+		preferred "ChST", so lower-case letters are now allowed.
+		Also, POSIX from 2001 on relaxed the rule to allow
+		'<code>-</code>', '<code>+</code>',
+		and alphanumeric characters from the portable character set
+		in the current locale.  In practice ASCII alphanumerics and
+		'<code>+</code>' and '<code>-</code>' are safe in all locales.
+
+		In other words, in the C locale the POSIX extended regular
+		expression <code>[-+[:alnum:]]{3,}</code> should match
+		the abbreviation.
+		This guarantees that all abbreviations could have been
+		specified by a POSIX TZ string.
+  </li>
+  <li>
+	Use abbreviations that are in common use among English-speakers,
+		e.g. 'EST' for Eastern Standard Time in North America.
+		We assume that applications translate them to other languages
+		as part of the normal localization process; for example,
+		a French application might translate 'EST' to 'HNE'.
+  </li>
+  <li>
+	For zones whose times are taken from a city's longitude, use the
+		traditional <var>x</var>MT notation, e.g. 'PMT' for
+		Paris Mean Time.
+		The only name like this in current use is 'GMT'.
+  </li>
+  <li>
+	Use 'LMT' for local mean time of locations before the introduction
+		of standard time; see "<a href="#scope">Scope of the
+		tz database</a>".
+  </li>
+  <li>
+	If there is no common English abbreviation, use numeric offsets like
+		<code>-</code>05 and <code>+</code>0830 that are
+		generated by zic's <code>%z</code> notation.
+  </li>
+  <li>
+	Use current abbreviations for older timestamps to avoid confusion.
+		For example, in 1910 a common English abbreviation for UT +01
+		in central Europe was 'MEZ' (short for both "Middle European
+		Zone" and for "Mitteleuropäische Zeit" in German).  Nowadays
+		'CET' ("Central European Time") is more common in English, and
+		the database uses 'CET' even for circa-1910 timestamps as this
+		is less confusing for modern users and avoids the need for
+		determining when 'CET' supplanted 'MEZ' in common usage.
+  </li>
+  <li>
+	Use a consistent style in a zone's history.  For example, if a zone's
+		history tends to use numeric abbreviations and a particular
+		entry could go either way, use a numeric abbreviation.
+  </li>
+</ul>
+    [The remaining guidelines predate the introduction of <code>%z</code>.
+    They are problematic as they mean tz data entries invent
+    notation rather than record it.  These guidelines are now
+    deprecated and the plan is to gradually move to <code>%z</code> for
+    inhabited locations and to "<code>-</code>00" for uninhabited locations.]
+<ul>
+  <li>
+	If there is no common English abbreviation, abbreviate the English
+		translation of the usual phrase used by native speakers.
+		If this is not available or is a phrase mentioning the country
+		(e.g. "Cape Verde Time"), then:
+	<ul>
+	  <li>
+		When a country is identified with a single or principal zone,
+			append 'T' to the country's ISO	code, e.g. 'CVT' for
+			Cape Verde Time.  For summer time append 'ST';
+			for double summer time append 'DST'; etc.
+	  </li>
+	  <li>
+		Otherwise, take the first three letters of an English place
+			name identifying each zone and append 'T', 'ST', etc.
+			as before; e.g. 'CHAST' for CHAtham Summer Time.
+	  </li>
+	</ul>
+  </li>
+  <li>
+	Use UT (with time zone abbreviation '<code>-</code>00') for
+		locations while uninhabited.  The leading
+		'<code>-</code>' is a flag that the time
+		zone is in some sense undefined; this notation is
+		derived from Internet RFC 3339.
+  </li>
+</ul>
+<p>
+Application writers should note that these abbreviations are ambiguous
+in practice: e.g. 'CST' has a different meaning in China than
+it does in the United States.  In new applications, it's often better
+to use numeric UT offsets like '<code>-</code>0600' instead of time zone
+abbreviations like 'CST'; this avoids the ambiguity.
+</p>
+  </section>
+
+
+  <section>
+    <h2 id="accuracy">Accuracy of the tz database</h2>
+<p>
+The tz database is not authoritative, and it surely has errors.
+Corrections are welcome and encouraged; see the file CONTRIBUTING.
+Users requiring authoritative data should consult national standards
+bodies and the references cited in the database's comments.
+</p>
+
+<p>
+Errors in the tz database arise from many sources:
+</p>
+<ul>
+  <li>
+   The tz database predicts future timestamps, and current predictions
+   will be incorrect after future governments change the rules.
+   For example, if today someone schedules a meeting for 13:00 next
+   October 1, Casablanca time, and tomorrow Morocco changes its
+   daylight saving rules, software can mess up after the rule change
+   if it blithely relies on conversions made before the change.
+  </li>
+  <li>
+   The pre-1970 entries in this database cover only a tiny sliver of how
+   clocks actually behaved; the vast majority of the necessary
+   information was lost or never recorded.  Thousands more zones would
+   be needed if the tz database's scope were extended to cover even
+   just the known or guessed history of standard time; for example,
+   the current single entry for France would need to split into dozens
+   of entries, perhaps hundreds.  And in most of the world even this
+   approach would be misleading due to widespread disagreement or
+   indifference about what times should be observed.  In her 2015 book
+   <cite>The Global Transformation of Time, 1870-1950</cite>, Vanessa Ogle writes
+   "Outside of Europe and North America there was no system of time
+   zones at all, often not even a stable landscape of mean times,
+   prior to the middle decades of the twentieth century".  See:
+   Timothy Shenk, <a
+   href="https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanessa-ogle">Booked:
+   A Global History of Time</a>. <cite>Dissent</cite> 2015-12-17.
+  </li>
+  <li>
+   Most of the pre-1970 data entries come from unreliable sources, often
+   astrology books that lack citations and whose compilers evidently
+   invented entries when the true facts were unknown, without
+   reporting which entries were known and which were invented.
+   These books often contradict each other or give implausible entries,
+   and on the rare occasions when they are checked they are
+   typically found to be incorrect.
+  </li>
+  <li>
+   For the UK the tz database relies on years of first-class work done by
+   Joseph Myers and others; see
+   "<a href="https://www.polyomino.org.uk/british-time/">History of
+   legal time in Britain</a>".
+   Other countries are not done nearly as well.
+  </li>
+  <li>
+   Sometimes, different people in the same city would maintain clocks
+   that differed significantly.  Railway time was used by railroad
+   companies (which did not always agree with each other),
+   church-clock time was used for birth certificates, etc.
+   Often this was merely common practice, but sometimes it was set by law.
+   For example, from 1891 to 1911 the UT offset in France was legally
+   0:09:21 outside train stations and 0:04:21 inside.
+  </li>
+  <li>
+   Although a named location in the tz database stands for the
+   containing region, its pre-1970 data entries are often accurate for
+   only a small subset of that region.  For example, <code>Europe/London</code>
+   stands for the United Kingdom, but its pre-1847 times are valid
+   only for locations that have London's exact meridian, and its 1847
+   transition to GMT is known to be valid only for the L&amp;NW and the
+   Caledonian railways.
+  </li>
+  <li>
+   The tz database does not record the earliest time for which a zone's
+   data entries are thereafter valid for every location in the region.
+   For example, <code>Europe/London</code> is valid for all locations in its
+   region after GMT was made the standard time, but the date of
+   standardization (1880-08-02) is not in the tz database, other than
+   in commentary.  For many zones the earliest time of validity is
+   unknown.
+  </li>
+  <li>
+   The tz database does not record a region's boundaries, and in many
+   cases the boundaries are not known.  For example, the zone
+   <code>America/Kentucky/Louisville</code> represents a region around
+   the city of
+   Louisville, the boundaries of which are unclear.
+  </li>
+  <li>
+   Changes that are modeled as instantaneous transitions in the tz
+   database were often spread out over hours, days, or even decades.
+  </li>
+  <li>
+   Even if the time is specified by law, locations sometimes
+   deliberately flout the law.
+  </li>
+  <li>
+   Early timekeeping practices, even assuming perfect clocks, were
+   often not specified to the accuracy that the tz database requires.
+  </li>
+  <li>
+   Sometimes historical timekeeping was specified more precisely
+   than what the tz database can handle.  For example, from 1909 to
+   1937 Netherlands clocks were legally UT +00:19:32.13, but the tz
+   database cannot represent the fractional second.
+  </li>
+  <li>
+   Even when all the timestamp transitions recorded by the tz database
+   are correct, the tz rules that generate them may not faithfully
+   reflect the historical rules.  For example, from 1922 until World
+   War II the UK moved clocks forward the day following the third
+   Saturday in April unless that was Easter, in which case it moved
+   clocks forward the previous Sunday.  Because the tz database has no
+   way to specify Easter, these exceptional years are entered as
+   separate tz Rule lines, even though the legal rules did not change.
+  </li>
+  <li>
+   The tz database models pre-standard time using the proleptic Gregorian
+   calendar and local mean time (LMT), but many people used other
+   calendars and other timescales.  For example, the Roman Empire used
+   the Julian calendar, and had 12 varying-length daytime hours with a
+   non-hour-based system at night.
+  </li>
+  <li>
+   Early clocks were less reliable, and data entries do not represent
+   clock error.
+  </li>
+  <li>
+   The tz database assumes Universal Time (UT) as an origin, even
+   though UT is not standardized for older timestamps.  In the tz
+   database commentary, UT denotes a family of time standards that
+   includes Coordinated Universal Time (UTC) along with other variants
+   such as UT1 and GMT, with days starting at midnight.  Although UT
+   equals UTC for modern timestamps, UTC was not defined until 1960,
+   so commentary uses the more-general abbreviation UT for timestamps
+   that might predate 1960.  Since UT, UT1, etc. disagree slightly,
+   and since pre-1972 UTC seconds varied in length, interpretation of
+   older timestamps can be problematic when subsecond accuracy is
+   needed.
+  </li>
+  <li>
+   Civil time was not based on atomic time before 1972, and we don't
+   know the history of earth's rotation accurately enough to map SI
+   seconds to historical solar time to more than about one-hour
+   accuracy.  See: Stephenson FR, Morrison LV, Hohenkerk CY.
+   <a href="http://dx.doi.org/10.1098/rspa.2016.0404">Measurement
+   of the Earth's rotation: 720 BC to AD 2015</a>.
+   <cite>Proc Royal Soc A</cite>. 2016 Dec 7;472:20160404.
+   Also see: Espenak F. <a
+   href="https://eclipse.gsfc.nasa.gov/SEhelp/uncertainty2004.html">Uncertainty
+   in Delta T (ΔT)</a>.
+  </li>
+  <li>
+   The relationship between POSIX time (that is, UTC but ignoring leap
+   seconds) and UTC is not agreed upon after 1972.  Although the POSIX
+   clock officially stops during an inserted leap second, at least one
+   proposed standard has it jumping back a second instead; and in
+   practice POSIX clocks more typically either progress glacially during
+   a leap second, or are slightly slowed while near a leap second.
+  </li>
+  <li>
+   The tz database does not represent how uncertain its information is.
+   Ideally it would contain information about when data entries are
+   incomplete or dicey.  Partial temporal knowledge is a field of
+   active research, though, and it's not clear how to apply it here.
+  </li>
+</ul>
+<p>
+In short, many, perhaps most, of the tz database's pre-1970 and future
+timestamps are either wrong or misleading.  Any attempt to pass the
+tz database off as the definition of time should be unacceptable to
+anybody who cares about the facts.  In particular, the tz database's
+LMT offsets should not be considered meaningful, and should not prompt
+creation of zones merely because two locations differ in LMT or
+transitioned to standard time at different dates.
+</p>
+  </section>
+
+
+  <section>
+    <h2 id="functions">Time and date functions</h2>
+<p>
+The tz code contains time and date functions that are upwards
+compatible with those of POSIX.
+</p>
+
+<p>
+POSIX has the following properties and limitations.
+</p>
+<ul>
+  <li>
+    <p>
+	In POSIX, time display in a process is controlled by the
+	environment variable TZ.  Unfortunately, the POSIX TZ string takes
+	a form that is hard to describe and is error-prone in practice.
+	Also, POSIX TZ strings can't deal with other (for example, Israeli)
+	daylight saving time rules, or situations where more than two
+	time zone abbreviations are used in an area.
+    </p>
+    <p>
+      The POSIX TZ string takes the following form:
+    </p>
+    <p>
+      <var>stdoffset</var>[<var>dst</var>[<var>offset</var>][<code>,</code><var>date</var>[<code>/</code><var>time</var>]<code>,</code><var>date</var>[<code>/</code><var>time</var>]]]
+    </p>
+    <p>
+	where:
+    <dl>
+      <dt><var>std</var> and <var>dst</var></dt><dd>
+		are 3 or more characters specifying the standard
+		and daylight saving time (DST) zone names.
+		Starting with POSIX.1-2001, <var>std</var>
+		and <var>dst</var> may also be
+		in a quoted form like '<code>&lt;UTC+10&gt;</code>'; this allows
+		"<code>+</code>" and "<code>-</code>" in the names.
+      </dd>
+      <dt><var>offset</var></dt><dd>
+		is of the form
+		'<code>[&plusmn;]<var>hh</var>:[<var>mm</var>[:<var>ss</var>]]</code>'
+		and specifies the offset west of UT.  '<var>hh</var>'
+		may be a single digit; 0&le;<var>hh</var>&le;24.
+		The default DST offset is one hour ahead of standard time.
+      </dd>
+      <dt><var>date</var>[<code>/</code><var>time</var>]<code>,</code><var>date</var>[<code>/</code><var>time</var>]</dt><dd>
+		specifies the beginning and end of DST.  If this is absent,
+		the system supplies its own rules for DST, and these can
+		differ from year to year; typically US DST rules are used.
+      </dd>
+      <dt><var>time</var></dt><dd>
+		takes the form
+		'<var>hh</var><code>:</code>[<var>mm</var>[<code>:</code><var>ss</var>]]'
+		and defaults to 02:00.
+		This is the same format as the offset, except that a
+		leading '<code>+</code>' or '<code>-</code>' is not allowed.
+      </dd>
+      <dt><var>date</var></dt><dd>
+		takes one of the following forms:
+	<dl>
+	  <dt>J<var>n</var> (1&le;<var>n</var>&le;365)</dt><dd>
+			origin-1 day number not counting February 29
+          </dd>
+	  <dt><var>n</var> (0&le;<var>n</var>&le;365)</dt><dd>
+			origin-0 day number counting February 29 if present
+          </dd>
+	  <dt><code>M</code><var>m</var><code>.</code><var>n</var><code>.</code><var>d</var> (0[Sunday]&le;<var>d</var>&le;6[Saturday], 1&le;<var>n</var>&le;5, 1&le;<var>m</var>&le;12)</dt><dd>
+			for the <var>d</var>th day of
+			week <var>n</var> of month <var>m</var> of the
+			year, where week 1 is the first week in which
+			day <var>d</var> appears, and '<code>5</code>'
+			stands for the last week in which
+			day <var>d</var> appears
+			(which may be either the 4th or 5th week).
+			Typically, this is the only useful form;
+			the <var>n</var>
+			and <code>J</code><var>n</var> forms are
+			rarely used.
+	  </dd>
+</dl>
+</dd>
+</dl>
+	Here is an example POSIX TZ string for New Zealand after 2007.
+	It says that standard time (NZST) is 12 hours ahead of UTC,
+	and that daylight saving time (NZDT) is observed from September's
+	last Sunday at 02:00 until April's first Sunday at 03:00:
+
+        <pre><code>TZ='NZST-12NZDT,M9.5.0,M4.1.0/3'</code></pre>
+
+	This POSIX TZ string is hard to remember, and mishandles some
+	timestamps before 2008.  With this package you can use this
+	instead:
+
+	<pre><code>TZ='Pacific/Auckland'</code></pre>
+  </li>
+  <li>
+	POSIX does not define the exact meaning of TZ values like
+	"<code>EST5EDT</code>".
+	Typically the current US DST rules are used to interpret such values,
+	but this means that the US DST rules are compiled into each program
+	that does time conversion.  This means that when US time conversion
+	rules change (as in the United States in 1987), all programs that
+	do time conversion must be recompiled to ensure proper results.
+  </li>
+  <li>
+	The TZ environment variable is process-global, which makes it hard
+	to write efficient, thread-safe applications that need access
+	to multiple time zones.
+  </li>
+  <li>
+	In POSIX, there's no tamper-proof way for a process to learn the
+	system's best idea of local wall clock.  (This is important for
+	applications that an administrator wants used only at certain
+	times &ndash;
+	without regard to whether the user has fiddled the TZ environment
+	variable.  While an administrator can "do everything in UTC" to get
+	around the problem, doing so is inconvenient and precludes handling
+	daylight saving time shifts - as might be required to limit phone
+	calls to off-peak hours.)
+  </li>
+  <li>
+	POSIX provides no convenient and efficient way to determine the UT
+	offset and time zone abbreviation of arbitrary timestamps,
+	particularly for time zone settings that do not fit into the
+	POSIX model.
+  </li>
+  <li>
+	POSIX requires that systems ignore leap seconds.
+  </li>
+  <li>
+	The tz code attempts to support all the <code>time_t</code>
+	implementations allowed by POSIX.  The <code>time_t</code>
+	type represents a nonnegative count of
+	seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds.
+	In practice, <code>time_t</code> is usually a signed 64- or
+	32-bit integer; 32-bit signed <code>time_t</code> values stop
+	working after 2038-01-19 03:14:07 UTC, so
+	new implementations these days typically use a signed 64-bit integer.
+	Unsigned 32-bit integers are used on one or two platforms,
+	and 36-bit and 40-bit integers are also used occasionally.
+	Although earlier POSIX versions allowed <code>time_t</code> to be a
+	floating-point type, this was not supported by any practical
+	systems, and POSIX.1-2013 and the tz code both
+	require <code>time_t</code>
+	to be an integer type.
+  </li>
+</ul>
+<p>
+These are the extensions that have been made to the POSIX functions:
+</p>
+<ul>
+  <li>
+    <p>
+	The TZ environment variable is used in generating the name of a file
+	from which time zone information is read (or is interpreted a la
+	POSIX); TZ is no longer constrained to be a three-letter time zone
+	name followed by a number of hours and an optional three-letter
+	daylight time zone name.  The daylight saving time rules to be used
+	for a particular time zone are encoded in the time zone file;
+	the format of the file allows U.S., Australian, and other rules to be
+	encoded, and allows for situations where more than two time zone
+	abbreviations are used.
+    </p>
+    <p>
+	It was recognized that allowing the TZ environment variable to
+	take on values such as '<code>America/New_York</code>' might
+	cause "old" programs
+	(that expect TZ to have a certain form) to operate incorrectly;
+	consideration was given to using some other environment variable
+	(for example, TIMEZONE) to hold the string used to generate the
+	time zone information file name.  In the end, however, it was decided
+	to continue using TZ: it is widely used for time zone purposes;
+	separately maintaining both TZ and TIMEZONE seemed a nuisance;
+	and systems where "new" forms of TZ might cause problems can simply
+	use TZ values such as "<code>EST5EDT</code>" which can be used both by
+	"new" programs (a la POSIX) and "old" programs (as zone names and
+	offsets).
+    </p>
+</li>
+<li>
+	The code supports platforms with a UT offset member
+	in <code>struct tm</code>,
+	e.g., <code>tm_gmtoff</code>.
+</li>
+<li>
+	The code supports platforms with a time zone abbreviation member in
+	<code>struct tm</code>, e.g., <code>tm_zone</code>.
+</li>
+<li>
+	Since the TZ environment variable can now be used to control time
+	conversion, the <code>daylight</code>
+	and <code>timezone</code> variables are no longer needed.
+	(These variables are defined and set by <code>tzset</code>;
+	however, their values will not be used
+	by <code>localtime</code>.)
+</li>
+<li>
+	Functions <code>tzalloc</code>, <code>tzfree</code>,
+	<code>localtime_rz</code>, and <code>mktime_z</code> for
+	more-efficient thread-safe applications that need to use
+	multiple time zones.  The <code>tzalloc</code>
+	and <code>tzfree</code> functions allocate and free objects of
+	type <code>timezone_t</code>, and <code>localtime_rz</code>
+	and <code>mktime_z</code> are like <code>localtime_r</code>
+	and <code>mktime</code> with an extra
+	<code>timezone_t</code> argument.  The functions were inspired
+	by NetBSD.
+</li>
+<li>
+	A function <code>tzsetwall</code> has been added to arrange
+	for the system's
+	best approximation to local wall clock time to be delivered by
+	subsequent calls to <code>localtime</code>.  Source code for portable
+	applications that "must" run on local wall clock time should call
+	<code>tzsetwall</code>; if such code is moved to "old" systems that don't
+	provide tzsetwall, you won't be able to generate an executable program.
+	(These time zone functions also arrange for local wall clock time to be
+	used if tzset is called &ndash; directly or indirectly &ndash;
+	and there's no TZ
+	environment variable; portable applications should not, however, rely
+	on this behavior since it's not the way SVR2 systems behave.)
+</li>
+<li>
+	Negative <code>time_t</code> values are supported, on systems
+	where <code>time_t</code> is signed.
+</li>
+<li>
+	These functions can account for leap seconds, thanks to Bradley White.
+</li>
+</ul>
+<p>
+Points of interest to folks with other systems:
+</p>
+<ul>
+  <li>
+	Code compatible with this package is already part of many platforms,
+	including GNU/Linux, Android, the BSDs, Chromium OS, Cygwin, AIX, iOS,
+	BlackBery 10, macOS, Microsoft Windows, OpenVMS, and Solaris.
+	On such hosts, the primary use of this package
+	is to update obsolete time zone rule tables.
+	To do this, you may need to compile the time zone compiler
+	'<code>zic</code>' supplied with this package instead of using
+	the system '<code>zic</code>', since the format
+	of <code>zic</code>'s input is occasionally extended, and a
+	platform may still be shipping an older <code>zic</code>.
+  </li>
+  <li>
+	The UNIX Version 7 <code>timezone</code> function is not
+	present in this package;
+	it's impossible to reliably map timezone's arguments (a "minutes west
+	of GMT" value and a "daylight saving time in effect" flag) to a
+	time zone abbreviation, and we refuse to guess.
+	Programs that in the past used the timezone function may now examine
+	<code>localtime(&amp;clock)-&gt;tm_zone</code>
+	(if <code>TM_ZONE</code> is defined) or
+	<code>tzname[localtime(&amp;clock)-&gt;tm_isdst]</code>
+	(if <code>HAVE_TZNAME</code> is defined)
+	to learn the correct time zone abbreviation to use.
+  </li>
+  <li>
+	The 4.2BSD <code>gettimeofday</code> function is not used in
+	this package.
+	This formerly let users obtain the current UTC offset and DST flag,
+	but this functionality was removed in later versions of BSD.
+  </li>
+  <li>
+	In SVR2, time conversion fails for near-minimum or near-maximum
+	<code>time_t</code> values when doing conversions for places
+	that don't use UT.
+	This package takes care to do these conversions correctly.
+	A comment in the source code tells how to get compatibly wrong
+	results.
+  </li>
+</ul>
+<p>
+The functions that are conditionally compiled
+if <code>STD_INSPIRED</code> is defined
+should, at this point, be looked on primarily as food for thought.  They are
+not in any sense "standard compatible" &ndash; some are not, in fact,
+specified in <em>any</em> standard.  They do, however, represent responses of
+various authors to
+standardization proposals.
+</p>
+
+<p>
+Other time conversion proposals, in particular the one developed by folks at
+Hewlett Packard, offer a wider selection of functions that provide capabilities
+beyond those provided here.  The absence of such functions from this package
+is not meant to discourage the development, standardization, or use of such
+functions.  Rather, their absence reflects the decision to make this package
+contain valid extensions to POSIX, to ensure its broad acceptability.  If
+more powerful time conversion functions can be standardized, so much the
+better.
+</p>
+  </section>
+
+
+  <section>
+    <h2 id="stability">Interface stability</h2>
+<p>
+The tz code and data supply the following interfaces:
+</p>
+<ul>
+  <li>
+   A set of zone names as per "<a href="#naming">Names of time zone
+   rules</a>" above.
+  </li>
+  <li>
+   Library functions described in "<a href="#functions">Time and date
+   functions</a>" above.
+  </li>
+  <li>
+   The programs <code>tzselect</code>, <code>zdump</code>,
+   and <code>zic</code>, documented in their man pages.
+  </li>
+  <li>
+   The format of <code>zic</code> input files, documented in
+   the <code>zic</code> man page.
+  </li>
+  <li>
+   The format of <code>zic</code> output files, documented in
+   the <code>tzfile</code> man page.
+  </li>
+  <li>
+   The format of zone table files, documented in <code>zone1970.tab</code>.
+  </li>
+  <li>
+   The format of the country code file, documented in <code>iso3166.tab</code>.
+  </li>
+  <li>
+   The version number of the code and data, as the first line of
+   the text file '<code>version</code>' in each release.
+  </li>
+</ul>
+<p>
+Interface changes in a release attempt to preserve compatibility with
+recent releases.  For example, tz data files typically do not rely on
+recently-added <code>zic</code> features, so that users can run
+older <code>zic</code> versions to process newer data
+files.  <a href="tz-link.htm">Sources for time zone and daylight
+saving time data</a> describes how
+releases are tagged and distributed.
+</p>
+
+<p>
+Interfaces not listed above are less stable.  For example, users
+should not rely on particular UT offsets or abbreviations for
+timestamps, as data entries are often based on guesswork and these
+guesses may be corrected or improved.
+</p>
+  </section>
+
+
+  <section>
+    <h2 id="calendar">Calendrical issues</h2>
+<p>
+Calendrical issues are a bit out of scope for a time zone database,
+but they indicate the sort of problems that we would run into if we
+extended the time zone database further into the past.  An excellent
+resource in this area is Nachum Dershowitz and Edward M. Reingold,
+<cite><a href="https://www.cs.tau.ac.il/~nachum/calendar-book/third-edition/">Calendrical
+Calculations: Third Edition</a></cite>, Cambridge University Press (2008).
+Other information and sources are given in the file '<samp>calendars</samp>'
+in the tz distribution.  They sometimes disagree.
+</p>
+  </section>
+
+
+  <section>
+    <h2 id="planets">Time and time zones on other planets</h2>
+<p>
+Some people's work schedules use Mars time.  Jet Propulsion Laboratory
+(JPL) coordinators have kept Mars time on and off at least since 1997
+for the Mars Pathfinder mission.  Some of their family members have
+also adapted to Mars time.  Dozens of special Mars watches were built
+for JPL workers who kept Mars time during the Mars Exploration
+Rovers mission (2004).  These timepieces look like normal Seikos and
+Citizens but use Mars seconds rather than terrestrial seconds.
+</p>
+
+<p>
+A Mars solar day is called a "sol" and has a mean period equal to
+about 24 hours 39 minutes 35.244 seconds in terrestrial time.  It is
+divided into a conventional 24-hour clock, so each Mars second equals
+about 1.02749125 terrestrial seconds.
+</p>
+
+<p>
+The prime meridian of Mars goes through the center of the crater
+Airy-0, named in honor of the British astronomer who built the
+Greenwich telescope that defines Earth's prime meridian.  Mean solar
+time on the Mars prime meridian is called Mars Coordinated Time (MTC).
+</p>
+
+<p>
+Each landed mission on Mars has adopted a different reference for
+solar time keeping, so there is no real standard for Mars time zones.
+For example, the Mars Exploration Rover project (2004) defined two
+time zones "Local Solar Time A" and "Local Solar Time B" for its two
+missions, each zone designed so that its time equals local true solar
+time at approximately the middle of the nominal mission.  Such a "time
+zone" is not particularly suited for any application other than the
+mission itself.
+</p>
+
+<p>
+Many calendars have been proposed for Mars, but none have achieved
+wide acceptance.  Astronomers often use Mars Sol Date (MSD) which is a
+sequential count of Mars solar days elapsed since about 1873-12-29
+12:00 GMT.
+</p>
+
+<p>
+In our solar system, Mars is the planet with time and calendar most
+like Earth's.  On other planets, Sun-based time and calendars would
+work quite differently.  For example, although Mercury's sidereal
+rotation period is 58.646 Earth days, Mercury revolves around the Sun
+so rapidly that an observer on Mercury's equator would see a sunrise
+only every 175.97 Earth days, i.e., a Mercury year is 0.5 of a Mercury
+day.  Venus is more complicated, partly because its rotation is
+slightly retrograde: its year is 1.92 of its days.  Gas giants like
+Jupiter are trickier still, as their polar and equatorial regions
+rotate at different rates, so that the length of a day depends on
+latitude.  This effect is most pronounced on Neptune, where the day is
+about 12 hours at the poles and 18 hours at the equator.
+</p>
+
+<p>
+Although the tz database does not support time on other planets, it is
+documented here in the hopes that support will be added eventually.
+</p>
+
+<p>
+Sources:
+</p>
+<ul>
+  <li>
+Michael Allison and Robert Schmunk,
+"<a href="https://www.giss.nasa.gov/tools/mars24/help/notes.html">Technical
+Notes on Mars Solar Time as Adopted by the Mars24 Sunclock</a>"
+(2012-08-08).
+  </li>
+  <li>
+Jia-Rui Chong,
+"<a href="http://articles.latimes.com/2004/jan/14/science/sci-marstime14">Workdays
+Fit for a Martian</a>", Los Angeles Times
+(2004-01-14), pp A1, A20-A21.
+  </li>
+  <li>
+Tom Chmielewski,
+"<a href="https://www.theatlantic.com/technology/archive/2015/02/jet-lag-is-worse-on-mars/386033/">Jet
+Lag Is Worse on Mars</a>", The Atlantic (2015-02-26)
+  </li>
+  <li>
+Matt Williams,
+"<a href="https://www.universetoday.com/37481/days-of-the-planets/">How
+long is a day on the other planets of the solar system?</a>"
+(2017-04-27).
+  </li>
+</ul>
+  </section>
+
+  <footer>
+    <hr>
+This file is in the public domain, so clarified as of 2009-05-17 by
+Arthur David Olson.
+  </footer>
+</body>
+</html>
diff --git a/contrib/tzdata/version b/contrib/tzdata/version
index c5bbdc4ead5d..198e36de73e0 100644
--- a/contrib/tzdata/version
+++ b/contrib/tzdata/version
@@ -1 +1 @@
-2017b
+2017c
diff --git a/contrib/tzdata/zishrink.awk b/contrib/tzdata/zishrink.awk
new file mode 100644
index 000000000000..02c883a62620
--- /dev/null
+++ b/contrib/tzdata/zishrink.awk
@@ -0,0 +1,156 @@
+# Convert tzdata source into a smaller version of itself.
+
+# Contributed by Paul Eggert.  This file is in the public domain.
+
+# This is not a general-purpose converter; it is designed for current tzdata.
+# 'zic' should treat this script's output as if it were identical to
+# this script's input.
+
+
+# Return a new rule name.
+# N_RULE_NAMES keeps track of how many rule names have been generated.
+
+function gen_rule_name(alphabet, base, rule_name, n, digit)
+{
+  alphabet = ""
+  alphabet = alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+  alphabet = alphabet "abcdefghijklmnopqrstuvwxyz"
+  alphabet = alphabet "!$%&'()*+,./:;<=>?@[\\]^_`{|}~"
+  base = length(alphabet)
+  rule_name = ""
+  n = n_rule_names++
+
+  do {
+    n -= rule_name && n <= base
+    digit = n % base
+    rule_name = substr(alphabet, digit + 1, 1) rule_name
+    n = (n - digit) / base
+  } while (n);
+
+  return rule_name
+}
+
+# Process an input line and save it for later output.
+
+function process_input_line(line, field, end, i, n, startdef)
+{
+  # Remove comments, normalize spaces, and append a space to each line.
+  sub(/#.*/, "", line)
+  line = line " "
+  gsub(/[[:space:]]+/, " ", line)
+
+  # Abbreviate keywords.  Do not abbreviate "Link" to just "L",
+  # as pre-2017c zic erroneously diagnoses "Li" as ambiguous.
+  sub(/^Link /, "Li ", line)
+  sub(/^Rule /, "R ", line)
+  sub(/^Zone /, "Z ", line)
+
+  # SystemV rules are not needed.
+  if (line ~ /^R SystemV /) return
+
+  # Replace FooAsia rules with the same rules without "Asia", as they
+  # are duplicates.
+  if (match(line, /[^ ]Asia /)) {
+    if (line ~ /^R /) return
+    line = substr(line, 1, RSTART) substr(line, RSTART + 5)
+  }
+
+  # Abbreviate times.
+  while (match(line, /[: ]0+[0-9]/))
+    line = substr(line, 1, RSTART) substr(line, RSTART + RLENGTH - 1)
+  while (match(line, /:0[^:]/))
+    line = substr(line, 1, RSTART - 1) substr(line, RSTART + 2)
+
+  # Abbreviate weekday names.  Do not abbreviate "Sun" and "Sat", as
+  # pre-2017c zic erroneously diagnoses "Su" and "Sa" as ambiguous.
+  while (match(line, / (last)?(Mon|Wed|Fri)[ <>]/)) {
+    end = RSTART + RLENGTH
+    line = substr(line, 1, end - 4) substr(line, end - 1)
+  }
+  while (match(line, / (last)?(Tue|Thu)[ <>]/)) {
+    end = RSTART + RLENGTH
+    line = substr(line, 1, end - 3) substr(line, end - 1)
+  }
+
+  # Abbreviate "max", "only" and month names.
+  # Do not abbreviate "min", as pre-2017c zic erroneously diagnoses "mi"
+  # as ambiguous.
+  gsub(/ max /, " ma ", line)
+  gsub(/ only /, " o ", line)
+  gsub(/ Jan /, " Ja ", line)
+  gsub(/ Feb /, " F ", line)
+  gsub(/ Apr /, " Ap ", line)
+  gsub(/ Aug /, " Au ", line)
+  gsub(/ Sep /, " S ", line)
+  gsub(/ Oct /, " O ", line)
+  gsub(/ Nov /, " N ", line)
+  gsub(/ Dec /, " D ", line)
+
+  # Strip leading and trailing space.
+  sub(/^ /, "", line)
+  sub(/ $/, "", line)
+
+  # Remove unnecessary trailing zero fields.
+  sub(/ 0+$/, "", line)
+
+  # Remove unnecessary trailing days-of-month "1".
+  if (match(line, /[[:alpha:]] 1$/))
+    line = substr(line, 1, RSTART)
+
+  # Remove unnecessary trailing " Ja" (for January).
+  sub(/ Ja$/, "", line)
+
+  n = split(line, field)
+
+  # Abbreviate rule names.
+  i = field[1] == "Z" ? 4 : field[1] == "Li" ? 0 : 2
+  if (i && field[i] ~ /^[^-+0-9]/) {
+    if (!rule[field[i]])
+      rule[field[i]] = gen_rule_name()
+    field[i] = rule[field[i]]
+  }
+
+  # If this zone supersedes an earlier one, delete the earlier one
+  # from the saved output lines.
+  startdef = ""
+  if (field[1] == "Z")
+    zonename = startdef = field[2]
+  else if (field[1] == "Li")
+    zonename = startdef = field[3]
+  else if (field[1] == "R")
+    zonename = ""
+  if (startdef) {
+    i = zonedef[startdef]
+    if (i) {
+      do
+	output_line[i - 1] = ""
+      while (output_line[i++] ~ /^[-+0-9]/);
+    }
+  }
+  zonedef[zonename] = nout + 1
+
+  # Save the line for later output.
+  line = field[1]
+  for (i = 2; i <= n; i++)
+    line = line " " field[i]
+  output_line[nout++] = line
+}
+
+function output_saved_lines(i)
+{
+  for (i = 0; i < nout; i++)
+    if (output_line[i])
+      print output_line[i]
+}
+
+BEGIN {
+  print "# This zic input file is in the public domain."
+}
+
+/^[[:space:]]*[^#[:space:]]/ {
+  process_input_line($0)
+}
+
+END {
+  output_saved_lines()
+}
diff --git a/contrib/tzdata/zone.tab b/contrib/tzdata/zone.tab
index 204048cc5a63..2d0b26b7d658 100644
--- a/contrib/tzdata/zone.tab
+++ b/contrib/tzdata/zone.tab
@@ -186,7 +186,7 @@ GB	+513030-0000731	Europe/London
 GD	+1203-06145	America/Grenada
 GE	+4143+04449	Asia/Tbilisi
 GF	+0456-05220	America/Cayenne
-GG	+4927-00232	Europe/Guernsey
+GG	+492717-0023210	Europe/Guernsey
 GH	+0533-00013	Africa/Accra
 GI	+3608-00521	Europe/Gibraltar
 GL	+6411-05144	America/Godthab	Greenland (most areas)
@@ -221,7 +221,7 @@ IQ	+3321+04425	Asia/Baghdad
 IR	+3540+05126	Asia/Tehran
 IS	+6409-02151	Atlantic/Reykjavik
 IT	+4154+01229	Europe/Rome
-JE	+4912-00207	Europe/Jersey
+JE	+491101-0020624	Europe/Jersey
 JM	+175805-0764736	America/Jamaica
 JO	+3157+03556	Asia/Amman
 JP	+353916+1394441	Asia/Tokyo
diff --git a/contrib/tzdata/zone1970.tab b/contrib/tzdata/zone1970.tab
index b5fd7fc7d31f..bb0357631562 100644
--- a/contrib/tzdata/zone1970.tab
+++ b/contrib/tzdata/zone1970.tab
@@ -2,7 +2,7 @@
 #
 # This file is in the public domain.
 #
-# From Paul Eggert (2014-07-31):
+# From Paul Eggert (2017-10-01):
 # This file contains a table where each row stands for a zone where
 # civil time stamps have agreed since 1970.  Columns are separated by
 # a single tab.  Lines beginning with '#' are comments.  All text uses
@@ -16,7 +16,7 @@
 #     either +-DDMM+-DDDMM or +-DDMMSS+-DDDMMSS,
 #     first latitude (+ is north), then longitude (+ is east).
 # 3.  Zone name used in value of TZ environment variable.
-#     Please see the 'Theory' file for how zone names are chosen.
+#     Please see the theory.html file for how zone names are chosen.
 #     If multiple zones overlap a country, each has a row in the
 #     table, with each column 1 containing the country code.
 # 4.  Comments; present if and only if a country has multiple zones.
@@ -317,10 +317,11 @@ RU	+6445+17729	Asia/Anadyr	MSK+09 - Bering Sea
 SA,KW,YE	+2438+04643	Asia/Riyadh
 SB	-0932+16012	Pacific/Guadalcanal
 SC	-0440+05528	Indian/Mahe
-SD,SS	+1536+03232	Africa/Khartoum
+SD	+1536+03232	Africa/Khartoum
 SE	+5920+01803	Europe/Stockholm
 SG	+0117+10351	Asia/Singapore
 SR	+0550-05510	America/Paramaribo
+SS	+0451+03137	Africa/Juba
 SV	+1342-08912	America/El_Salvador
 SY	+3330+03618	Asia/Damascus
 TC	+2128-07108	America/Grand_Turk