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Diffstat (limited to 'usr.sbin/ntp/ntpd/leap-seconds')
| -rw-r--r-- | usr.sbin/ntp/ntpd/leap-seconds | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/usr.sbin/ntp/ntpd/leap-seconds b/usr.sbin/ntp/ntpd/leap-seconds new file mode 100644 index 000000000000..649a22c6278f --- /dev/null +++ b/usr.sbin/ntp/ntpd/leap-seconds @@ -0,0 +1,120 @@ +# ATOMIC TIME +# Coordinated Universal Time (UTC) is the reference time scale derived +# from The "Temps Atomique International" (TAI) calculated by the Bureau +# International des Poids et Mesures (BIPM) using a worldwide network of atomic +# clocks. UTC differs from TAI by an integer number of seconds; it is the basis +# of all activities in the world. +# +# +# ASTRONOMICAL TIME (UT1) is the time scale based on the rate of rotation of the earth. +# It is now mainly derived from Very Long Baseline Interferometry (VLBI). The various +# irregular fluctuations progressively detected in the rotation rate of the Earth led +# in 1972 to the replacement of UT1 by UTC as the reference time scale. +# +# +# LEAP SECOND +# Atomic clocks are more stable than the rate of the earth's rotation since the latter +# undergoes a full range of geophysical perturbations at various time scales: lunisolar +# and core-mantle torques, atmospheric and oceanic effects, etc. +# Leap seconds are needed to keep the two time scales in agreement, i.e. UT1-UTC smaller +# than 0.9 seconds. Therefore, when necessary a "leap second" is applied to UTC. +# Since the adoption of this system in 1972 it has been necessary to add a number of seconds to UTC, +# firstly due to the initial choice of the value of the second (1/86400 mean solar day of +# the year 1820) and secondly to the general slowing down of the Earth's rotation. It is +# theoretically possible to have a negative leap second (a second removed from UTC), but so far, +# all leap seconds have been positive (a second has been added to UTC). Based on what we know about +# the earth's rotation, it is unlikely that we will ever have a negative leap second. +# +# +# HISTORY +# The first leap second was added on June 30, 1972. Until the year 2000, it was necessary in average to add a +# leap second at a rate of 1 to 2 years. Since the year 2000 leap seconds are introduced with an +# average interval of 3 to 4 years due to the acceleration of the Earth's rotation speed. +# +# +# RESPONSIBILITY OF THE DECISION TO INTRODUCE A LEAP SECOND IN UTC +# The decision to introduce a leap second in UTC is the responsibility of the Earth Orientation Center of +# the International Earth Rotation and reference System Service (IERS). This center is located at Paris +# Observatory. According to international agreements, leap seconds should be scheduled only for certain dates: +# first preference is given to the end of December and June, and second preference at the end of March +# and September. Since the introduction of leap seconds in 1972, only dates in June and December were used. +# +# Questions or comments to: +# Christian Bizouard: christian.bizouard@obspm.fr +# Earth orientation Center of the IERS +# Paris Observatory, France +# +# +# +# COPYRIGHT STATUS OF THIS FILE +# This file is in the public domain. +# +# +# VALIDITY OF THE FILE +# It is important to express the validity of the file. These next two dates are +# given in units of seconds since 1900.0. +# +# 1) Last update of the file. +# +# Updated through IERS Bulletin C (https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat) +# +# The following line shows the last update of this file in NTP timestamp: +# +#$ 3960835200 +# +# 2) Expiration date of the file given on a semi-annual basis: last June or last December +# +# File expires on 28 June 2026 +# +# Expire date in NTP timestamp: +# +#@ 3991593600 +# +# +# LIST OF LEAP SECONDS +# NTP timestamp (X parameter) is the number of seconds since 1900.0 +# +# MJD: The Modified Julian Day number. MJD = X/86400 + 15020 +# +# DTAI: The difference DTAI= TAI-UTC in units of seconds +# It is the quantity to add to UTC to get the time in TAI +# +# Day Month Year : epoch in clear +# +#NTP Time DTAI Day Month Year +# +2272060800 10 # 1 Jan 1972 +2287785600 11 # 1 Jul 1972 +2303683200 12 # 1 Jan 1973 +2335219200 13 # 1 Jan 1974 +2366755200 14 # 1 Jan 1975 +2398291200 15 # 1 Jan 1976 +2429913600 16 # 1 Jan 1977 +2461449600 17 # 1 Jan 1978 +2492985600 18 # 1 Jan 1979 +2524521600 19 # 1 Jan 1980 +2571782400 20 # 1 Jul 1981 +2603318400 21 # 1 Jul 1982 +2634854400 22 # 1 Jul 1983 +2698012800 23 # 1 Jul 1985 +2776982400 24 # 1 Jan 1988 +2840140800 25 # 1 Jan 1990 +2871676800 26 # 1 Jan 1991 +2918937600 27 # 1 Jul 1992 +2950473600 28 # 1 Jul 1993 +2982009600 29 # 1 Jul 1994 +3029443200 30 # 1 Jan 1996 +3076704000 31 # 1 Jul 1997 +3124137600 32 # 1 Jan 1999 +3345062400 33 # 1 Jan 2006 +3439756800 34 # 1 Jan 2009 +3550089600 35 # 1 Jul 2012 +3644697600 36 # 1 Jul 2015 +3692217600 37 # 1 Jan 2017 +# +# A hash code has been generated to be able to verify the integrity +# of this file. For more information about using this hash code, +# please see the readme file in the 'source' directory : +# https://hpiers.obspm.fr/iers/bul/bulc/ntp/sources/README +# +#h 49db2447 571e5e1b 2f002a53 9c8da8e4 39b8e49e |