mirror of
https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
synced 2024-11-24 17:44:17 +01:00
121 lines
4.9 KiB
Plaintext
121 lines
4.9 KiB
Plaintext
# ATOMIC TIME.
|
|
# The 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 lead
|
|
# 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 rotation since the latter
|
|
# undergoes a full range of geophysical perturbations at various time scales: lunisolar
|
|
# and core-mantle torques, atmospheric and oceanic effetcs, etc.
|
|
# Leap seconds are needed to keep the two time scales in agreement, i.e. UT1-UTC smaller
|
|
# than 0.9 second. 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
|
|
# theorically 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 yhe 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 rotation speed.
|
|
#
|
|
#
|
|
# RESPONSABILITY 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 only be scheduled 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:
|
|
#
|
|
#$ 3913697179
|
|
#
|
|
# 2) Expiration date of the file given on a semi-annual basis: last June or last December
|
|
#
|
|
# File expires on 28 December 2024
|
|
#
|
|
# Expire date in NTP timestamp:
|
|
#
|
|
#@ 3944332800
|
|
#
|
|
#
|
|
# 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 9dac5845 8acd32c0 2947d462 daf4a943 f58d9391
|