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diff --git a/zic.8.txt b/zic.8.txt index cf86f584ca30..acef001bbafd 100644 --- a/zic.8.txt +++ b/zic.8.txt @@ -18,74 +18,75 @@ OPTIONS --help Output short usage message and exit. -b bloat - Output backward-compatibility data as specified by bloat. If - bloat is fat, generate additional data entries that work around - potential bugs or incompatibilities in older software, such as + Output backward-compatibility data as specified by bloat. If + bloat is fat, generate additional data entries that work around + potential bugs or incompatibilities in older software, such as software that mishandles the 64-bit generated data. If bloat is - slim, keep the output files small; this can help check for the - bugs and incompatibilities. The default is slim, as software - that mishandles 64-bit data typically mishandles timestamps - after the year 2038 anyway. Also see the -r option for another + slim, keep the output files small; this can help check for the + bugs and incompatibilities. The default is slim, as software + that mishandles 64-bit data typically mishandles timestamps + after the year 2038 anyway. Also see the -r option for another way to alter output size. -d directory - Create time conversion information files in the named directory + Create time conversion information files in the named directory rather than in the standard directory named below. -l timezone - Use timezone as local time. zic will act as if the input + Use timezone as local time. zic will act as if the input contained a link line of the form - Link timezone localtime + Link timezone localtime If timezone is -, any already-existing link is removed. -L leapsecondfilename - Read leap second information from the file with the given name. - If this option is not used, no leap second information appears + Read leap second information from the file with the given name. + If this option is not used, no leap second information appears in output files. -p timezone - Use timezone's rules when handling nonstandard TZ strings like - "EET-2EEST" that lack transition rules. zic will act as if the + Use timezone's rules when handling nonstandard TZ strings like + "EET-2EEST" that lack transition rules. zic will act as if the input contained a link line of the form - Link timezone posixrules + Link timezone posixrules - Unless timezone is "-", this option is obsolete and poorly - supported. Among other things it should not be used for - timestamps after the year 2037, and it should not be combined - with -b slim if timezone's transitions are at standard time or - Universal Time (UT) instead of local time. + If timezone is "-" (the default), any already-existing link is + removed. - If timezone is -, any already-existing link is removed. + Unless timezone is "-", this option is obsolete and poorly + supported. Among other things it should not be used for + timestamps after the year 2037, and it should not be combined + with -b slim if timezone's transitions are at standard time or + Universal Time (UT) instead of local time. -r [@lo][/@hi] - Limit the applicability of output files to timestamps in the + Limit the applicability of output files to timestamps in the range from lo (inclusive) to hi (exclusive), where lo and hi are - possibly signed decimal counts of seconds since the Epoch - (1970-01-01 00:00:00 UTC). Omitted counts default to extreme + possibly signed decimal counts of seconds since the Epoch + (1970-01-01 00:00:00 UTC). Omitted counts default to extreme values. The output files use UT offset 0 and abbreviation "-00" - in place of the omitted timestamp data. For example, "zic -r - @0" omits data intended for negative timestamps (i.e., before - the Epoch), and "zic -r @0/@2147483648" outputs data intended - only for nonnegative timestamps that fit into 31-bit signed - integers. On platforms with GNU date, "zic -r @$(date +%s)" - omits data intended for past timestamps. Although this option - typically reduces the output file's size, the size can increase - due to the need to represent the timestamp range boundaries, - particularly if hi causes a TZif file to contain explicit - entries for pre-hi transitions rather than concisely - representing them with an extended POSIX TZ string. Also see - the -b slim option for another way to shrink output size. + in place of the omitted timestamp data. For example, "zic -r + @0" omits data intended for negative timestamps (i.e., before + the Epoch), and "zic -r @0/@2147483648" outputs data intended + only for nonnegative timestamps that fit into 31-bit signed + integers. On platforms with GNU date, "zic -r @$(date +%s)" + omits data intended for past timestamps. Although this option + typically reduces the output file's size, the size can increase + due to the need to represent the timestamp range boundaries, + particularly if hi causes a TZif file to contain explicit + entries for pre-hi transitions rather than concisely + representing them with an extended POSIX.1-2017 TZ string. Also + see the -b slim option for another way to shrink output size. - -R @hi Generate redundant trailing explicit transitions for timestamps + -R @hi Generate redundant trailing explicit transitions for timestamps that occur less than hi seconds since the Epoch, even though the transitions could be more concisely represented via the extended - POSIX TZ string. This option does not affect the represented - timestamps. Although it accommodates nonstandard TZif readers - that ignore the extended POSIX TZ string, it increases the size - of the altered output files. + POSIX.1-2017 TZ string. This option does not affect the + represented timestamps. Although it accommodates nonstandard + TZif readers that ignore the extended POSIX.1-2017 TZ string, it + increases the size of the altered output files. -t file When creating local time information, put the configuration link @@ -96,356 +97,352 @@ OPTIONS The input specifies a link to a link, something not supported by some older parsers, including zic itself through release 2022e. - A year that appears in a data file is outside the range of + A year that appears in a data file is outside the range of representable years. A time of 24:00 or more appears in the input. Pre-1998 versions - of zic prohibit 24:00, and pre-2007 versions prohibit times + of zic prohibit 24:00, and pre-2007 versions prohibit times greater than 24:00. - A rule goes past the start or end of the month. Pre-2004 + A rule goes past the start or end of the month. Pre-2004 versions of zic prohibit this. A time zone abbreviation uses a %z format. Pre-2015 versions of zic do not support this. - A timestamp contains fractional seconds. Pre-2018 versions of + A timestamp contains fractional seconds. Pre-2018 versions of zic do not support this. The input contains abbreviations that are mishandled by pre-2018 - versions of zic due to a longstanding coding bug. These - abbreviations include "L" for "Link", "mi" for "min", "Sa" for + versions of zic due to a longstanding coding bug. These + abbreviations include "L" for "Link", "mi" for "min", "Sa" for "Sat", and "Su" for "Sun". - The output file does not contain all the information about the - long-term future of a timezone, because the future cannot be - summarized as an extended POSIX TZ string. For example, as of - 2023 this problem occurs for Morocco's daylight-saving rules, as - these rules are based on predictions for when Ramadan will be - observed, something that an extended POSIX TZ string cannot - represent. + The output file does not contain all the information about the + long-term future of a timezone, because the future cannot be + summarized as an extended POSIX.1-2017 TZ string. For example, + as of 2023 this problem occurs for Morocco's daylight-saving + rules, as these rules are based on predictions for when Ramadan + will be observed, something that an extended POSIX.1-2017 TZ + string cannot represent. - The output contains data that may not be handled properly by - client code designed for older zic output formats. These + The output contains data that may not be handled properly by + client code designed for older zic output formats. These compatibility issues affect only timestamps before 1970 or after the start of 2038. - The output contains a truncated leap second table, which can - cause some older TZif readers to misbehave. This can occur if - the -L option is used, and either an Expires line is present or + The output contains a truncated leap second table, which can + cause some older TZif readers to misbehave. This can occur if + the -L option is used, and either an Expires line is present or the -r option is also used. - The output file contains more than 1200 transitions, which may - be mishandled by some clients. The current reference client - supports at most 2000 transitions; pre-2014 versions of the + The output file contains more than 1200 transitions, which may + be mishandled by some clients. The current reference client + supports at most 2000 transitions; pre-2014 versions of the reference client support at most 1200 transitions. - A time zone abbreviation has fewer than 3 or more than 6 - characters. POSIX requires at least 3, and requires + A time zone abbreviation has fewer than 3 or more than 6 + characters. POSIX requires at least 3, and requires implementations to support at least 6. An output file name contains a byte that is not an ASCII letter, - "-", "/", or "_"; or it contains a file name component that + "-", "/", or "_"; or it contains a file name component that contains more than 14 bytes or that starts with "-". FILES - Input files use the format described in this section; output files use + Input files use the format described in this section; output files use tzfile(5) format. - Input files should be text files, that is, they should be a series of - zero or more lines, each ending in a newline byte and containing at - most 2048 bytes counting the newline, and without any NUL bytes. The - input text's encoding is typically UTF-8 or ASCII; it should have a - unibyte representation for the POSIX Portable Character Set (PPCS) + Input files should be text files, that is, they should be a series of + zero or more lines, each ending in a newline byte and containing at + most 2048 bytes counting the newline, and without any NUL bytes. The + input text's encoding is typically UTF-8 or ASCII; it should have a + unibyte representation for the POSIX Portable Character Set (PPCS) <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap06 - .html> and the encoding's non-unibyte characters should consist - entirely of non-PPCS bytes. Non-PPCS characters typically occur only + .html> and the encoding's non-unibyte characters should consist + entirely of non-PPCS bytes. Non-PPCS characters typically occur only in comments: although output file names and time zone abbreviations can - contain nearly any character, other software will work better if these + contain nearly any character, other software will work better if these are limited to the restricted syntax described under the -v option. - Input lines are made up of fields. Fields are separated from one - another by one or more white space characters. The white space - characters are space, form feed, carriage return, newline, tab, and - vertical tab. Leading and trailing white space on input lines is - ignored. An unquoted sharp character (#) in the input introduces a - comment which extends to the end of the line the sharp character - appears on. White space characters and sharp characters may be + Input lines are made up of fields. Fields are separated from one + another by one or more white space characters. The white space + characters are space, form feed, carriage return, newline, tab, and + vertical tab. Leading and trailing white space on input lines is + ignored. An unquoted sharp character (#) in the input introduces a + comment which extends to the end of the line the sharp character + appears on. White space characters and sharp characters may be enclosed in double quotes (") if they're to be used as part of a field. - Any line that is blank (after comment stripping) is ignored. Nonblank + Any line that is blank (after comment stripping) is ignored. Nonblank lines are expected to be of one of three types: rule lines, zone lines, and link lines. - Names must be in English and are case insensitive. They appear in + Names must be in English and are case insensitive. They appear in several contexts, and include month and weekday names and keywords such - as maximum, only, Rolling, and Zone. A name can be abbreviated by - omitting all but an initial prefix; any abbreviation must be + as maximum, only, Rolling, and Zone. A name can be abbreviated by + omitting all but an initial prefix; any abbreviation must be unambiguous in context. A rule line has the form - Rule NAME FROM TO - IN ON AT SAVE LETTER/S + Rule NAME FROM TO - IN ON AT SAVE LETTER/S For example: - Rule US 1967 1973 - Apr lastSun 2:00w 1:00d D + Rule US 1967 1973 - Apr lastSun 2:00w 1:00d D The fields that make up a rule line are: - NAME Gives the name of the rule set that contains this line. The - name must start with a character that is neither an ASCII digit - nor "-" nor "+". To allow for future extensions, an unquoted - name should not contain characters from the set - "!$%&'()*,/:;<=>?@[\]^`{|}~". + NAME Gives the name of the rule set that contains this line. The + name must start with a character that is neither an ASCII digit + nor "-" nor "+". To allow for future extensions, an unquoted + name should not contain characters from the set + "!$%&'()*,/:;<=>?@[\]^`{|}~". - FROM Gives the first year in which the rule applies. Any signed - integer year can be supplied; the proleptic Gregorian calendar - is assumed, with year 0 preceding year 1. The word minimum (or - an abbreviation) means the indefinite past. The word maximum - (or an abbreviation) means the indefinite future. Rules can - describe times that are not representable as time values, with - the unrepresentable times ignored; this allows rules to be - portable among hosts with differing time value types. + FROM Gives the first year in which the rule applies. Any signed + integer year can be supplied; the proleptic Gregorian calendar + is assumed, with year 0 preceding year 1. Rules can describe + times that are not representable as time values, with the + unrepresentable times ignored; this allows rules to be portable + among hosts with differing time value types. - TO Gives the final year in which the rule applies. In addition to - minimum and maximum (as above), the word only (or an - abbreviation) may be used to repeat the value of the FROM - field. + TO Gives the final year in which the rule applies. The word + maximum (or an abbreviation) means the indefinite future, and + the word only (or an abbreviation) may be used to repeat the + value of the FROM field. - - Is a reserved field and should always contain "-" for - compatibility with older versions of zic. It was previously - known as the TYPE field, which could contain values to allow a - separate script to further restrict in which "types" of years - the rule would apply. + - Is a reserved field and should always contain "-" for + compatibility with older versions of zic. It was previously + known as the TYPE field, which could contain values to allow a + separate script to further restrict in which "types" of years + the rule would apply. - IN Names the month in which the rule takes effect. Month names - may be abbreviated. + IN Names the month in which the rule takes effect. Month names may + be abbreviated. - ON Gives the day on which the rule takes effect. Recognized forms - include: + ON Gives the day on which the rule takes effect. Recognized forms + include: - 5 the fifth of the month - lastSun the last Sunday in the month - lastMon the last Monday in the month - Sun>=8 first Sunday on or after the eighth - Sun<=25 last Sunday on or before the 25th + 5 the fifth of the month + lastSun the last Sunday in the month + lastMon the last Monday in the month + Sun>=8 first Sunday on or after the eighth + Sun<=25 last Sunday on or before the 25th - A weekday name (e.g., Sunday) or a weekday name preceded by - "last" (e.g., lastSunday) may be abbreviated or spelled out in - full. There must be no white space characters within the ON - field. The "<=" and ">=" constructs can result in a day in the - neighboring month; for example, the IN-ON combination "Oct - Sun>=31" stands for the first Sunday on or after October 31, - even if that Sunday occurs in November. + A weekday name (e.g., Sunday) or a weekday name preceded by + "last" (e.g., lastSunday) may be abbreviated or spelled out in + full. There must be no white space characters within the ON + field. The "<=" and ">=" constructs can result in a day in the + neighboring month; for example, the IN-ON combination "Oct + Sun>=31" stands for the first Sunday on or after October 31, + even if that Sunday occurs in November. - AT Gives the time of day at which the rule takes effect, relative - to 00:00, the start of a calendar day. Recognized forms - include: + AT Gives the time of day at which the rule takes effect, relative + to 00:00, the start of a calendar day. Recognized forms + include: - 2 time in hours - 2:00 time in hours and minutes - 01:28:14 time in hours, minutes, and seconds - 00:19:32.13 time with fractional seconds - 12:00 midday, 12 hours after 00:00 - 15:00 3 PM, 15 hours after 00:00 - 24:00 end of day, 24 hours after 00:00 - 260:00 260 hours after 00:00 - -2:30 2.5 hours before 00:00 - - equivalent to 0 + 2 time in hours + 2:00 time in hours and minutes + 01:28:14 time in hours, minutes, and seconds + 00:19:32.13 time with fractional seconds + 12:00 midday, 12 hours after 00:00 + 15:00 3 PM, 15 hours after 00:00 + 24:00 end of day, 24 hours after 00:00 + 260:00 260 hours after 00:00 + -2:30 2.5 hours before 00:00 + - equivalent to 0 - Although zic rounds times to the nearest integer second - (breaking ties to the even integer), the fractions may be - useful to other applications requiring greater precision. The - source format does not specify any maximum precision. Any of - these forms may be followed by the letter w if the given time - is local or "wall clock" time, s if the given time is standard - time without any adjustment for daylight saving, or u (or g or - z) if the given time is universal time; in the absence of an - indicator, local (wall clock) time is assumed. These forms - ignore leap seconds; for example, if a leap second occurs at - 00:59:60 local time, "1:00" stands for 3601 seconds after local - midnight instead of the usual 3600 seconds. The intent is that - a rule line describes the instants when a clock/calendar set to - the type of time specified in the AT field would show the - specified date and time of day. + Although zic rounds times to the nearest integer second + (breaking ties to the even integer), the fractions may be useful + to other applications requiring greater precision. The source + format does not specify any maximum precision. Any of these + forms may be followed by the letter w if the given time is local + or "wall clock" time, s if the given time is standard time + without any adjustment for daylight saving, or u (or g or z) if + the given time is universal time; in the absence of an + indicator, local (wall clock) time is assumed. These forms + ignore leap seconds; for example, if a leap second occurs at + 00:59:60 local time, "1:00" stands for 3601 seconds after local + midnight instead of the usual 3600 seconds. The intent is that + a rule line describes the instants when a clock/calendar set to + the type of time specified in the AT field would show the + specified date and time of day. - SAVE Gives the amount of time to be added to local standard time - when the rule is in effect, and whether the resulting time is - standard or daylight saving. This field has the same format as - the AT field except with a different set of suffix letters: s - for standard time and d for daylight saving time. The suffix - letter is typically omitted, and defaults to s if the offset is - zero and to d otherwise. Negative offsets are allowed; in - Ireland, for example, daylight saving time is observed in - winter and has a negative offset relative to Irish Standard - Time. The offset is merely added to standard time; for - example, zic does not distinguish a 10:30 standard time plus an - 0:30 SAVE from a 10:00 standard time plus a 1:00 SAVE. + SAVE Gives the amount of time to be added to local standard time when + the rule is in effect, and whether the resulting time is + standard or daylight saving. This field has the same format as + the AT field except with a different set of suffix letters: s + for standard time and d for daylight saving time. The suffix + letter is typically omitted, and defaults to s if the offset is + zero and to d otherwise. Negative offsets are allowed; in + Ireland, for example, daylight saving time is observed in winter + and has a negative offset relative to Irish Standard Time. The + offset is merely added to standard time; for example, zic does + not distinguish a 10:30 standard time plus an 0:30 SAVE from a + 10:00 standard time plus a 1:00 SAVE. LETTER/S - Gives the "variable part" (for example, the "S" or "D" in "EST" - or "EDT") of time zone abbreviations to be used when this rule - is in effect. If this field is "-", the variable part is null. + Gives the "variable part" (for example, the "S" or "D" in "EST" + or "EDT") of time zone abbreviations to be used when this rule + is in effect. If this field is "-", the variable part is null. A zone line has the form - Zone NAME STDOFF RULES FORMAT [UNTIL] + Zone NAME STDOFF RULES FORMAT [UNTIL] For example: - Zone Asia/Amman 2:00 Jordan EE%sT 2017 Oct 27 01:00 + Zone Asia/Amman 2:00 Jordan EE%sT 2017 Oct 27 01:00 The fields that make up a zone line are: - NAME The name of the timezone. This is the name used in creating the - time conversion information file for the timezone. It should not - contain a file name component "." or ".."; a file name component - is a maximal substring that does not contain "/". + NAME The name of the timezone. This is the name used in creating the + time conversion information file for the timezone. It should + not contain a file name component "." or ".."; a file name + component is a maximal substring that does not contain "/". - STDOFF - The amount of time to add to UT to get standard time, without any - adjustment for daylight saving. This field has the same format - as the AT and SAVE fields of rule lines, except without suffix - letters; begin the field with a minus sign if time must be - subtracted from UT. + STDOFF The amount of time to add to UT to get standard time, without + any adjustment for daylight saving. This field has the same + format as the AT and SAVE fields of rule lines, except without + suffix letters; begin the field with a minus sign if time must + be subtracted from UT. - RULES The name of the rules that apply in the timezone or, - alternatively, a field in the same format as a rule-line SAVE - column, giving the amount of time to be added to local standard - time and whether the resulting time is standard or daylight - saving. If this field is - then standard time always applies. - When an amount of time is given, only the sum of standard time - and this amount matters. + RULES The name of the rules that apply in the timezone or, + alternatively, a field in the same format as a rule-line SAVE + column, giving the amount of time to be added to local standard + time and whether the resulting time is standard or daylight + saving. If this field is - then standard time always applies. + When an amount of time is given, only the sum of standard time + and this amount matters. - FORMAT - The format for time zone abbreviations. The pair of characters - %s is used to show where the "variable part" of the time zone - abbreviation goes. Alternatively, a format can use the pair of - characters %z to stand for the UT offset in the form +-hh, - +-hhmm, or +-hhmmss, using the shortest form that does not lose - information, where hh, mm, and ss are the hours, minutes, and - seconds east (+) or west (-) of UT. Alternatively, a slash (/) - separates standard and daylight abbreviations. To conform to - POSIX, a time zone abbreviation should contain only alphanumeric - ASCII characters, "+" and "-". By convention, the time zone - abbreviation "-00" is a placeholder that means local time is - unspecified. + FORMAT The format for time zone abbreviations. The pair of characters + %s is used to show where the "variable part" of the time zone + abbreviation goes. Alternatively, a format can use the pair of + characters %z to stand for the UT offset in the form +-hh, + +-hhmm, or +-hhmmss, using the shortest form that does not lose + information, where hh, mm, and ss are the hours, minutes, and + seconds east (+) or west (-) of UT. Alternatively, a slash (/) + separates standard and daylight abbreviations. To conform to + POSIX, a time zone abbreviation should contain only alphanumeric + ASCII characters, "+" and "-". By convention, the time zone + abbreviation "-00" is a placeholder that means local time is + unspecified. - UNTIL The time at which the UT offset or the rule(s) change for a - location. It takes the form of one to four fields YEAR [MONTH - [DAY [TIME]]]. If this is specified, the time zone information - is generated from the given UT offset and rule change until the - time specified, which is interpreted using the rules in effect - just before the transition. The month, day, and time of day have - the same format as the IN, ON, and AT fields of a rule; trailing - fields can be omitted, and default to the earliest possible value - for the missing fields. + UNTIL The time at which the UT offset or the rule(s) change for a + location. It takes the form of one to four fields YEAR [MONTH + [DAY [TIME]]]. If this is specified, the time zone information + is generated from the given UT offset and rule change until the + time specified, which is interpreted using the rules in effect + just before the transition. The month, day, and time of day + have the same format as the IN, ON, and AT fields of a rule; + trailing fields can be omitted, and default to the earliest + possible value for the missing fields. - The next line must be a "continuation" line; this has the same - form as a zone line except that the string "Zone" and the name - are omitted, as the continuation line will place information - starting at the time specified as the "until" information in the - previous line in the file used by the previous line. - Continuation lines may contain "until" information, just as zone - lines do, indicating that the next line is a further - continuation. + The next line must be a "continuation" line; this has the same + form as a zone line except that the string "Zone" and the name + are omitted, as the continuation line will place information + starting at the time specified as the "until" information in the + previous line in the file used by the previous line. + Continuation lines may contain "until" information, just as zone + lines do, indicating that the next line is a further + continuation. - If a zone changes at the same instant that a rule would otherwise take - effect in the earlier zone or continuation line, the rule is ignored. - A zone or continuation line L with a named rule set starts with - standard time by default: that is, any of L's timestamps preceding L's - earliest rule use the rule in effect after L's first transition into - standard time. In a single zone it is an error if two rules take - effect at the same instant, or if two zone changes take effect at the + If a zone changes at the same instant that a rule would otherwise take + effect in the earlier zone or continuation line, the rule is ignored. + A zone or continuation line L with a named rule set starts with + standard time by default: that is, any of L's timestamps preceding L's + earliest rule use the rule in effect after L's first transition into + standard time. In a single zone it is an error if two rules take + effect at the same instant, or if two zone changes take effect at the same instant. - If a continuation line subtracts N seconds from the UT offset after a - transition that would be interpreted to be later if using the - continuation line's UT offset and rules, the "until" time of the - previous zone or continuation line is interpreted according to the - continuation line's UT offset and rules, and any rule that would - otherwise take effect in the next N seconds is instead assumed to take + If a continuation line subtracts N seconds from the UT offset after a + transition that would be interpreted to be later if using the + continuation line's UT offset and rules, the "until" time of the + previous zone or continuation line is interpreted according to the + continuation line's UT offset and rules, and any rule that would + otherwise take effect in the next N seconds is instead assumed to take effect simultaneously. For example: # Rule NAME FROM TO - IN ON AT SAVE LETTER/S Rule US 1967 2006 - Oct lastSun 2:00 0 S Rule US 1967 1973 - Apr lastSun 2:00 1:00 D - # Zone NAME STDOFF RULES FORMAT [UNTIL] - Zone America/Menominee -5:00 - EST 1973 Apr 29 2:00 - -6:00 US C%sT + # Zone NAME STDOFF RULES FORMAT [UNTIL] + Zone America/Menominee -5:00 - EST 1973 Apr 29 2:00 + -6:00 US C%sT - Here, an incorrect reading would be there were two clock changes on - 1973-04-29, the first from 02:00 EST (-05) to 01:00 CST (-06), and the + Here, an incorrect reading would be there were two clock changes on + 1973-04-29, the first from 02:00 EST (-05) to 01:00 CST (-06), and the second an hour later from 02:00 CST (-06) to 03:00 CDT (-05). However, zic interprets this more sensibly as a single transition from 02:00 CST (-05) to 02:00 CDT (-05). A link line has the form - Link TARGET LINK-NAME + Link TARGET LINK-NAME For example: - Link Europe/Istanbul Asia/Istanbul + Link Europe/Istanbul Asia/Istanbul - The TARGET field should appear as the NAME field in some zone line or - as the LINK-NAME field in some link line. The LINK-NAME field is used - as an alternative name for that zone; it has the same syntax as a zone - line's NAME field. Links can chain together, although the behavior is - unspecified if a chain of one or more links does not terminate in a - Zone name. A link line can appear before the line that defines the + The TARGET field should appear as the NAME field in some zone line or + as the LINK-NAME field in some link line. The LINK-NAME field is used + as an alternative name for that zone; it has the same syntax as a zone + line's NAME field. Links can chain together, although the behavior is + unspecified if a chain of one or more links does not terminate in a + Zone name. A link line can appear before the line that defines the link target. For example: Link Greenwich G_M_T Link Etc/GMT Greenwich Zone Etc/GMT 0 - GMT - The two links are chained together, and G_M_T, Greenwich, and Etc/GMT + The two links are chained together, and G_M_T, Greenwich, and Etc/GMT all name the same zone. - Except for continuation lines, lines may appear in any order in the - input. However, the behavior is unspecified if multiple zone or link + Except for continuation lines, lines may appear in any order in the + input. However, the behavior is unspecified if multiple zone or link lines define the same name. - The file that describes leap seconds can have leap lines and an + The file that describes leap seconds can have leap lines and an expiration line. Leap lines have the following form: - Leap YEAR MONTH DAY HH:MM:SS CORR R/S + Leap YEAR MONTH DAY HH:MM:SS CORR R/S For example: - Leap 2016 Dec 31 23:59:60 + S + Leap 2016 Dec 31 23:59:60 + S - The YEAR, MONTH, DAY, and HH:MM:SS fields tell when the leap second + The YEAR, MONTH, DAY, and HH:MM:SS fields tell when the leap second happened. The CORR field should be "+" if a second was added or "-" if - a second was skipped. The R/S field should be (an abbreviation of) - "Stationary" if the leap second time given by the other fields should - be interpreted as UTC or (an abbreviation of) "Rolling" if the leap - second time given by the other fields should be interpreted as local + a second was skipped. The R/S field should be (an abbreviation of) + "Stationary" if the leap second time given by the other fields should + be interpreted as UTC or (an abbreviation of) "Rolling" if the leap + second time given by the other fields should be interpreted as local (wall clock) time. - Rolling leap seconds were implemented back when it was not clear - whether common practice was rolling or stationary, with concerns that - one would see Times Square ball drops where there'd be a "3... 2... - 1... leap... Happy New Year" countdown, placing the leap second at - midnight New York time rather than midnight UTC. However, this - countdown style does not seem to have caught on, which means rolling - leap seconds are not used in practice; also, they are not supported if + Rolling leap seconds were implemented back when it was not clear + whether common practice was rolling or stationary, with concerns that + one would see Times Square ball drops where there'd be a "3... 2... + 1... leap... Happy New Year" countdown, placing the leap second at + midnight New York time rather than midnight UTC. However, this + countdown style does not seem to have caught on, which means rolling + leap seconds are not used in practice; also, they are not supported if the -r option is used. The expiration line, if present, has the form: - Expires YEAR MONTH DAY HH:MM:SS + Expires YEAR MONTH DAY HH:MM:SS For example: - Expires 2020 Dec 28 00:00:00 + Expires 2020 Dec 28 00:00:00 The YEAR, MONTH, DAY, and HH:MM:SS fields give the expiration timestamp in UTC for the leap second table. EXTENDED EXAMPLE - Here is an extended example of zic input, intended to illustrate many + Here is an extended example of zic input, intended to illustrate many of its features. # Rule NAME FROM TO - IN ON AT SAVE LETTER/S @@ -466,29 +463,29 @@ EXTENDED EXAMPLE Link Europe/Zurich Europe/Vaduz - In this example, the EU rules are for the European Union and for its - predecessor organization, the European Communities. The timezone is - named Europe/Zurich and it has the alias Europe/Vaduz. This example - says that Zurich was 34 minutes and 8 seconds east of UT until - 1853-07-16 at 00:00, when the legal offset was changed to 7 degrees 26 - minutes 22.50 seconds, which works out to 0:29:45.50; zic treats this - by rounding it to 0:29:46. After 1894-06-01 at 00:00 the UT offset - became one hour and Swiss daylight saving rules (defined with lines - beginning with "Rule Swiss") apply. From 1981 to the present, EU - daylight saving rules have applied, and the UTC offset has remained at + In this example, the EU rules are for the European Union and for its + predecessor organization, the European Communities. The timezone is + named Europe/Zurich and it has the alias Europe/Vaduz. This example + says that Zurich was 34 minutes and 8 seconds east of UT until + 1853-07-16 at 00:00, when the legal offset was changed to 7 degrees 26 + minutes 22.50 seconds, which works out to 0:29:45.50; zic treats this + by rounding it to 0:29:46. After 1894-06-01 at 00:00 the UT offset + became one hour and Swiss daylight saving rules (defined with lines + beginning with "Rule Swiss") apply. From 1981 to the present, EU + daylight saving rules have applied, and the UTC offset has remained at one hour. In 1941 and 1942, daylight saving time applied from the first Monday in - May at 01:00 to the first Monday in October at 02:00. The pre-1981 EU - daylight-saving rules have no effect here, but are included for + May at 01:00 to the first Monday in October at 02:00. The pre-1981 EU + daylight-saving rules have no effect here, but are included for completeness. Since 1981, daylight saving has begun on the last Sunday - in March at 01:00 UTC. Until 1995 it ended the last Sunday in - September at 01:00 UTC, but this changed to the last Sunday in October + in March at 01:00 UTC. Until 1995 it ended the last Sunday in + September at 01:00 UTC, but this changed to the last Sunday in October starting in 1996. - For purposes of display, "LMT" and "BMT" were initially used, - respectively. Since Swiss rules and later EU rules were applied, the - time zone abbreviation has been CET for standard time and CEST for + For purposes of display, "LMT" and "BMT" were initially used, + respectively. Since Swiss rules and later EU rules were applied, the + time zone abbreviation has been CET for standard time and CEST for daylight saving time. FILES @@ -499,15 +496,15 @@ FILES Default timezone information directory. NOTES - For areas with more than two types of local time, you may need to use - local standard time in the AT field of the earliest transition time's - rule to ensure that the earliest transition time recorded in the + For areas with more than two types of local time, you may need to use + local standard time in the AT field of the earliest transition time's + rule to ensure that the earliest transition time recorded in the compiled file is correct. - If, for a particular timezone, a clock advance caused by the start of - daylight saving coincides with and is equal to a clock retreat caused - by a change in UT offset, zic produces a single transition to daylight - saving at the new UT offset without any change in local (wall clock) + If, for a particular timezone, a clock advance caused by the start of + daylight saving coincides with and is equal to a clock retreat caused + by a change in UT offset, zic produces a single transition to daylight + saving at the new UT offset without any change in local (wall clock) time. To get separate transitions use multiple zone continuation lines specifying transition instants using universal time. |