94c2d487f1
Merge commit 'a5725262945a2971af3b808088217fe975e8364e' Changes: https://github.com/eggert/tz/blob/2021b/NEWS MFC after: 3 days
256 lines
10 KiB
Plaintext
256 lines
10 KiB
Plaintext
#
|
|
# In the following text, the symbol '#' introduces
|
|
# a comment, which continues from that symbol until
|
|
# the end of the line. A plain comment line has a
|
|
# whitespace character following the comment indicator.
|
|
# There are also special comment lines defined below.
|
|
# A special comment will always have a non-whitespace
|
|
# character in column 2.
|
|
#
|
|
# A blank line should be ignored.
|
|
#
|
|
# The following table shows the corrections that must
|
|
# be applied to compute International Atomic Time (TAI)
|
|
# from the Coordinated Universal Time (UTC) values that
|
|
# are transmitted by almost all time services.
|
|
#
|
|
# The first column shows an epoch as a number of seconds
|
|
# since 1 January 1900, 00:00:00 (1900.0 is also used to
|
|
# indicate the same epoch.) Both of these time stamp formats
|
|
# ignore the complexities of the time scales that were
|
|
# used before the current definition of UTC at the start
|
|
# of 1972. (See note 3 below.)
|
|
# The second column shows the number of seconds that
|
|
# must be added to UTC to compute TAI for any timestamp
|
|
# at or after that epoch. The value on each line is
|
|
# valid from the indicated initial instant until the
|
|
# epoch given on the next one or indefinitely into the
|
|
# future if there is no next line.
|
|
# (The comment on each line shows the representation of
|
|
# the corresponding initial epoch in the usual
|
|
# day-month-year format. The epoch always begins at
|
|
# 00:00:00 UTC on the indicated day. See Note 5 below.)
|
|
#
|
|
# Important notes:
|
|
#
|
|
# 1. Coordinated Universal Time (UTC) is often referred to
|
|
# as Greenwich Mean Time (GMT). The GMT time scale is no
|
|
# longer used, and the use of GMT to designate UTC is
|
|
# discouraged.
|
|
#
|
|
# 2. The UTC time scale is realized by many national
|
|
# laboratories and timing centers. Each laboratory
|
|
# identifies its realization with its name: Thus
|
|
# UTC(NIST), UTC(USNO), etc. The differences among
|
|
# these different realizations are typically on the
|
|
# order of a few nanoseconds (i.e., 0.000 000 00x s)
|
|
# and can be ignored for many purposes. These differences
|
|
# are tabulated in Circular T, which is published monthly
|
|
# by the International Bureau of Weights and Measures
|
|
# (BIPM). See www.bipm.org for more information.
|
|
#
|
|
# 3. The current definition of the relationship between UTC
|
|
# and TAI dates from 1 January 1972. A number of different
|
|
# time scales were in use before that epoch, and it can be
|
|
# quite difficult to compute precise timestamps and time
|
|
# intervals in those "prehistoric" days. For more information,
|
|
# consult:
|
|
#
|
|
# The Explanatory Supplement to the Astronomical
|
|
# Ephemeris.
|
|
# or
|
|
# Terry Quinn, "The BIPM and the Accurate Measurement
|
|
# of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
|
|
# July, 1991. <http://dx.doi.org/10.1109/5.84965>
|
|
# reprinted in:
|
|
# Christine Hackman and Donald B Sullivan (eds.)
|
|
# Time and Frequency Measurement
|
|
# American Association of Physics Teachers (1996)
|
|
# <http://tf.nist.gov/general/pdf/1168.pdf>, pp. 75-86
|
|
#
|
|
# 4. The decision to insert a leap second into UTC is currently
|
|
# the responsibility of the International Earth Rotation and
|
|
# Reference Systems Service. (The name was changed from the
|
|
# International Earth Rotation Service, but the acronym IERS
|
|
# is still used.)
|
|
#
|
|
# Leap seconds are announced by the IERS in its Bulletin C.
|
|
#
|
|
# See www.iers.org for more details.
|
|
#
|
|
# Every national laboratory and timing center uses the
|
|
# data from the BIPM and the IERS to construct UTC(lab),
|
|
# their local realization of UTC.
|
|
#
|
|
# Although the definition also includes the possibility
|
|
# of dropping seconds ("negative" leap seconds), this has
|
|
# never been done and is unlikely to be necessary in the
|
|
# foreseeable future.
|
|
#
|
|
# 5. If your system keeps time as the number of seconds since
|
|
# some epoch (e.g., NTP timestamps), then the algorithm for
|
|
# assigning a UTC time stamp to an event that happens during a positive
|
|
# leap second is not well defined. The official name of that leap
|
|
# second is 23:59:60, but there is no way of representing that time
|
|
# in these systems.
|
|
# Many systems of this type effectively stop the system clock for
|
|
# one second during the leap second and use a time that is equivalent
|
|
# to 23:59:59 UTC twice. For these systems, the corresponding TAI
|
|
# timestamp would be obtained by advancing to the next entry in the
|
|
# following table when the time equivalent to 23:59:59 UTC
|
|
# is used for the second time. Thus the leap second which
|
|
# occurred on 30 June 1972 at 23:59:59 UTC would have TAI
|
|
# timestamps computed as follows:
|
|
#
|
|
# ...
|
|
# 30 June 1972 23:59:59 (2287785599, first time): TAI= UTC + 10 seconds
|
|
# 30 June 1972 23:59:60 (2287785599,second time): TAI= UTC + 11 seconds
|
|
# 1 July 1972 00:00:00 (2287785600) TAI= UTC + 11 seconds
|
|
# ...
|
|
#
|
|
# If your system realizes the leap second by repeating 00:00:00 UTC twice
|
|
# (this is possible but not usual), then the advance to the next entry
|
|
# in the table must occur the second time that a time equivalent to
|
|
# 00:00:00 UTC is used. Thus, using the same example as above:
|
|
#
|
|
# ...
|
|
# 30 June 1972 23:59:59 (2287785599): TAI= UTC + 10 seconds
|
|
# 30 June 1972 23:59:60 (2287785600, first time): TAI= UTC + 10 seconds
|
|
# 1 July 1972 00:00:00 (2287785600,second time): TAI= UTC + 11 seconds
|
|
# ...
|
|
#
|
|
# in both cases the use of timestamps based on TAI produces a smooth
|
|
# time scale with no discontinuity in the time interval. However,
|
|
# although the long-term behavior of the time scale is correct in both
|
|
# methods, the second method is technically not correct because it adds
|
|
# the extra second to the wrong day.
|
|
#
|
|
# This complexity would not be needed for negative leap seconds (if they
|
|
# are ever used). The UTC time would skip 23:59:59 and advance from
|
|
# 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by
|
|
# 1 second at the same instant. This is a much easier situation to deal
|
|
# with, since the difficulty of unambiguously representing the epoch
|
|
# during the leap second does not arise.
|
|
#
|
|
# Some systems implement leap seconds by amortizing the leap second
|
|
# over the last few minutes of the day. The frequency of the local
|
|
# clock is decreased (or increased) to realize the positive (or
|
|
# negative) leap second. This method removes the time step described
|
|
# above. Although the long-term behavior of the time scale is correct
|
|
# in this case, this method introduces an error during the adjustment
|
|
# period both in time and in frequency with respect to the official
|
|
# definition of UTC.
|
|
#
|
|
# Questions or comments to:
|
|
# Judah Levine
|
|
# Time and Frequency Division
|
|
# NIST
|
|
# Boulder, Colorado
|
|
# Judah.Levine@nist.gov
|
|
#
|
|
# Last Update of leap second values: 8 July 2016
|
|
#
|
|
# The following line shows this last update date in NTP timestamp
|
|
# format. This is the date on which the most recent change to
|
|
# the leap second data was added to the file. This line can
|
|
# be identified by the unique pair of characters in the first two
|
|
# columns as shown below.
|
|
#
|
|
#$ 3676924800
|
|
#
|
|
# The NTP timestamps are in units of seconds since the NTP epoch,
|
|
# which is 1 January 1900, 00:00:00. The Modified Julian Day number
|
|
# corresponding to the NTP time stamp, X, can be computed as
|
|
#
|
|
# X/86400 + 15020
|
|
#
|
|
# where the first term converts seconds to days and the second
|
|
# term adds the MJD corresponding to the time origin defined above.
|
|
# The integer portion of the result is the integer MJD for that
|
|
# day, and any remainder is the time of day, expressed as the
|
|
# fraction of the day since 0 hours UTC. The conversion from day
|
|
# fraction to seconds or to hours, minutes, and seconds may involve
|
|
# rounding or truncation, depending on the method used in the
|
|
# computation.
|
|
#
|
|
# The data in this file will be updated periodically as new leap
|
|
# seconds are announced. In addition to being entered on the line
|
|
# above, the update time (in NTP format) will be added to the basic
|
|
# file name leap-seconds to form the name leap-seconds.<NTP TIME>.
|
|
# In addition, the generic name leap-seconds.list will always point to
|
|
# the most recent version of the file.
|
|
#
|
|
# This update procedure will be performed only when a new leap second
|
|
# is announced.
|
|
#
|
|
# The following entry specifies the expiration date of the data
|
|
# in this file in units of seconds since the origin at the instant
|
|
# 1 January 1900, 00:00:00. This expiration date will be changed
|
|
# at least twice per year whether or not a new leap second is
|
|
# announced. These semi-annual changes will be made no later
|
|
# than 1 June and 1 December of each year to indicate what
|
|
# action (if any) is to be taken on 30 June and 31 December,
|
|
# respectively. (These are the customary effective dates for new
|
|
# leap seconds.) This expiration date will be identified by a
|
|
# unique pair of characters in columns 1 and 2 as shown below.
|
|
# In the unlikely event that a leap second is announced with an
|
|
# effective date other than 30 June or 31 December, then this
|
|
# file will be edited to include that leap second as soon as it is
|
|
# announced or at least one month before the effective date
|
|
# (whichever is later).
|
|
# If an announcement by the IERS specifies that no leap second is
|
|
# scheduled, then only the expiration date of the file will
|
|
# be advanced to show that the information in the file is still
|
|
# current -- the update time stamp, the data and the name of the file
|
|
# will not change.
|
|
#
|
|
# Updated through IERS Bulletin C62
|
|
# File expires on: 28 June 2022
|
|
#
|
|
#@ 3865363200
|
|
#
|
|
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
|
|
#
|
|
# the following special comment contains the
|
|
# hash value of the data in this file computed
|
|
# use the secure hash algorithm as specified
|
|
# by FIPS 180-1. See the files in ~/pub/sha for
|
|
# the details of how this hash value is
|
|
# computed. Note that the hash computation
|
|
# ignores comments and whitespace characters
|
|
# in data lines. It includes the NTP values
|
|
# of both the last modification time and the
|
|
# expiration time of the file, but not the
|
|
# white space on those lines.
|
|
# the hash line is also ignored in the
|
|
# computation.
|
|
#
|
|
#h 599d45bf accd4b4f 8b60e46 49b623 7d13b825
|