[tz] Updated Eggert leap-seconds.list
Chris Woodbury
tzocd at yahoo.com
Wed Jan 8 20:43:20 UTC 2020
On the occasion of a new IERS Bulletin C, I present an
updated version of a public domain leap-second.list file.
# -=*( This file is in the public domain )*=-
# This NTP leap-second file was created with data obtained from
# the United States Naval Observatory (USNO) MAIA FTP server.
#
# Find it at: <ftp://maia.usno.navy.mil/ser7/leapsec.dat> (down)
# <ftp://cddis.gsfc.nasa.gov/pub/products/iers/leapsec.dat> (backup)
# Updated using information from IERS Bulletin C 59 (7 Jan 2020)
# Found at <ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat>
#
# IERS Bulletin C 59 did not announce a new leap-second.
#
# The last leap-second occurred on 1 Jan 2017 (3692217600)
# which was announced in IERS Bulletin C 52 on 6 July 2016.
#
# -=<*>=-
#
# This file is not produced by a national metrology laboratory.
# It *is* created using data from one:
#
# United States Naval Observatory (USNO)
# IERS Rapid Service/Prediction Center for Earth Orientation
# 3450 Massachusetts Ave NW, Washington, DC 20392
#
# It should be noted that anyone with proper information can
# generate an NTP leap-seconds.list file.
#
# The generation of this file was at the behest of Dr. Eggert
# on the occasion of a US government shutdown which resulted
# in a lack of an NIST generated file until late in January 2019.
#
# -=<*>=-
#
# The Network Time Protocol (NTP) keeps time in Coordinated
# Universal Time (UTC). UTC is a time scale based upon
# Standard International (SI) seconds and derived from Temps
# Atomique International (TAI). UTC is the de facto basis for
# legal time for much of the world since 1 Jan 1972 0h.
#
# [Le] Bureau International des Poids et Mesures (BIPM) tracks
# TAI, UT1, TE, UTC, etc. uses a weighted ensemble of 420+ atomic
# clocks at over 80+ national metrology laboratories worldwide
# to track time and Very-Long-Baseline Interferometry (VLBI)
# for precision millisecond pulsars timing and to track Earth's
# orientation in space. The origin of TAI has been agreed
# officially to coincide with UT1 on 1 January 1958 0h.
#
# For further information, read BIPM monograph "Time Scales"
# found at:
#
# <https://www.bipm.org/...
# utils/common/pdf/monographies-misc/Monographie1994-1.pdf>
#
# And "Coordinated Universal Time" at:
#
# <https://www.bipm.org/cc/CCTF/Allowed/18/CCTF_09-32_noteUTC.pdf>
#
# And, lastly:
#
# "Atomic Time Scales for Dynamical Astronomy" pp.51-56
#
# "How Can Millisecond Pulsars Improve the Long-Term Stability
# of Atomic Time Scales?", pp.57-60:
#
# Proceedings of the 6th European Frequency and Time Forum
# (17-19 March 1992)
#
# <http://www.eftf.org/proceedings/proceedingsEFTF1992.pdf>
#
# -=<*>=-
#
# Leap seconds are an official correction to UTC to keep it
# within 0.9 seconds of UT1; yet another time standard
# based upon the orientation of the earth in space (and the
# basis of legal time until 1972). IERS Bulletin A keeps
# track of and predicts the value of UT1-UTC.
#
# See: ftp://maia.usno.navy.mil/ser7/ser7.dat (down)
# ftp://cddis.gsfc.nasa.gov/pub/products/iers/ser7.dat (backup)
#
# The data kept in "leap-seconds.list" are used by the
# Network Time Protocol daemon (NTPd) to determine when to
# apply leap seconds to Coordinated Universal Time (UTC).
# "leap-seconds.list" is a symbolic link to the actual
# file name, leap-seconds.xxxxxxxxxx, where xxxxxxxxxx
# is derived from the NTP update timestamp (below).
#
# Theoretically, a leap second may be positive or negative.
# Realistically, negative leap seconds are unlikely to occur.
#
# All timestamps in this leap seconds file are encoded using the
# NTP epoch. These timestamps represent the number of seconds
# since 1 Jan 1900 0:00:00. This is Modified Julian Date (MJD)
# 15020 and Julian Date 2415020.5. There will be an unsigned
# 32-bit overflow to the second NTP era in 2036 (07 Feb 2036
# 06:28:16 UTC to be precise).
#
# A leap second datum consists of an NTP timestamp and the
# number of seconds difference between TAI and UTC (e.g.
# currently TAI-UTC is 37). UTC was established (at
# midnight) on 1 Jan 1972 0h with TAI-UTC started at 10.
# There was no mechanism prior to that time defining when
# to apply leap seconds.
#
# Note: the first datum in the leap-seconds.list file is
# *not* a leap-second; it denotes the definition of the
# UTC timescale.
#
# Leap-seconds rules are establish in:
#
# International Telecommunications Union-Recommendation (ITU-R)
# 460-6 (Standard-frequency and Time-Signal Emissions),
# Annex 1 (Time scales), Section 2 (Leap-Seconds).
#
# Note: Version 460-6 of the Recommendation is incorporated
# by reference in the [ITU] Radio Regulations.
#
# <http://www.itu.int/rec/R-REC-TF.460-6-200202-I/>
#
# Also note that Annex 1, Section 2.1 of this document contradicts
# the comments in Bulletin C regarding as to when a leap-second
# may be applied. i.e. As the last second of any UTC month.
# Preference is given to June and December and, secondarily, in
# March and September. (All have been in June or December.)
#
# Section 2.3: Delegates leap-second timing/dissemination to the
# International Earth Rotation and Reference System Service (IERS),
# (in its role as inheritor of Bureau International de l'Heure (BIH)).
#
# NTP Leap second files have an update time (#$). This is often
# the UTC zero (0) hour time of the day when the leap second file
# is built. [I am of the opinion] it should be updated whenever
# a new IERS Bulletin C is issued. CCW]
#
#$ 3787382231
#
# Leap second data have a lifetime. Traditionally, this ends on
# the twenty-eighth (28) day of the month six months after the
# period of time described in the latest IERS Bulletin C. This
# is the expiry time (#@).
#
# Updated through IERS Bulletin C 59 (7 Jan 2020)
# File expires on: 28 Jul 2020
#
#@ 3818102400
#
# Leap second files have a hash, as define in NIST's FIPS 180
# Secure Hash Standard (SHS), current revision 4 (FIPS 180-4).
#
# FIPS Publications: <http://csrc.nist.gov/publications/fips/>
# Direct Link: <http://dx.doi.org/10.6028/NIST.FIPS.180-4>
#
# It is based on an SHA[1] digest, created using the data
# portions of the file including leap second data and the update
# and expiry timestamps. All "white space" and comments are
# ignored in the computation thereof. The 160-bit SHA[1]
# digest polynomial are encoded in five hexadecimal grouping at
# the end of the file (#h). The hash itself is NOT included in
# the SHA[1]. It can also be calculated using GNU sha1sum which
# generates the same 160-bit digest, given the same data, in
# forty hexadecimal characters.
#
# NTP delta
#timestamp T Date of Change
#
2272060800 10 # 1 Jan 1972 (MJD 41317)
2287785600 11 # 1 Jul 1972 (MJD 41499)
2303683200 12 # 1 Jan 1973 (MJD 41683)
2335219200 13 # 1 Jan 1974 (MJD 42048)
2366755200 14 # 1 Jan 1975 (MJD 42413)
2398291200 15 # 1 Jan 1976 (MJD 42778)
2429913600 16 # 1 Jan 1977 (MJD 43144)
2461449600 17 # 1 Jan 1978 (MJD 43509)
2492985600 18 # 1 Jan 1979 (MJD 43874)
2524521600 19 # 1 Jan 1980 (MJD 44239)
2571782400 20 # 1 Jul 1981 (MJD 44786)
2603318400 21 # 1 Jul 1982 (MJD 45151)
2634854400 22 # 1 Jul 1983 (MJD 45516)
2698012800 23 # 1 Jul 1985 (MJD 46247)
2776982400 24 # 1 Jan 1988 (MJD 47161)
2840140800 25 # 1 Jan 1990 (MJD 47892)
2871676800 26 # 1 Jan 1991 (MJD 48257)
2918937600 27 # 1 Jul 1992 (MJD 48804)
2950473600 28 # 1 Jul 1993 (MJD 49169)
2982009600 29 # 1 Jul 1994 (MJD 49534)
3029443200 30 # 1 Jan 1996 (MJD 50083)
3076704000 31 # 1 Jul 1997 (MJD 50630)
3124137600 32 # 1 Jan 1999 (MJD 51179)
3345062400 33 # 1 Jan 2006 (MJD 53736)
3439756800 34 # 1 Jan 2009 (MJD 54832)
3550089600 35 # 1 Jul 2012 (MJD 56109)
3644697600 36 # 1 Jul 2015 (MJD 57204)
3692217600 37 # 1 Jan 2017 (MJD 57754)
#
#h 85073416 421bdd85 47662775 e154160c 4f1a3070
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