[tz] NIST leap-second file not yet updated
Tim Parenti
tim at timtimeonline.com
Mon Feb 15 17:14:52 UTC 2016
On 15 Feb 2016 11:39, Martin Burnicki wrote:
> please note the NIST leap-second file at ftp://time.nist.gov/pub/ has
> not yet been updated according to IERS bulletin C 51. It's still the
> version which has been published in July 2015, and will expire in June 2016.
>
> I saw that also tzdata2016a.tar.gz which has been published 2016-01-26
> still contains the old leap second file even though bulletin C 51 has
> already been published 2016-01-11.
I had the same thought.
I prepared the attached patch which uses the file from IERS shortly after the 2016-01-11 announcement, but was sitting on it while we waited for NIST, since the conversation at the time seemed to indicate that NIST was our preferred source. I think, though, that since IERS actually decides the leap seconds and seems to be updating their file more promptly, it might be worthwhile to consider switching to IERS as our canonical source for this file.
--
Tim Parenti
-------------- next part --------------
From 536069d9405c09b98e9cb331f79c59379eea7c31 Mon Sep 17 00:00:00 2001
From: Tim Parenti <tim at timtimeonline.com>
Date: Wed, 13 Jan 2016 16:01:13 -0500
Subject: No leap second on 2016-06-30.
* leap-seconds.list: Per IERS Bulletin C51 (2016-01-11), no leap second
on 2016-06-30. Update file from IERS.
https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.51
https://hpiers.obspm.fr/iers/bul/bulc/ntp/leap-seconds.list
---
leap-seconds.list | 365 +++++++++++++++++-------------------------------------
1 file changed, 116 insertions(+), 249 deletions(-)
diff --git a/leap-seconds.list b/leap-seconds.list
index 0a0bacb..3603b7d 100644
--- a/leap-seconds.list
+++ b/leap-seconds.list
@@ -1,249 +1,116 @@
-#
-# 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.
-#
-# 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 at nist.gov
-#
-# Last Update of leap second values: 5 January 2015
-#
-# 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.
-#
-#$ 3629404800
-#
-# 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 C50
-# File expires on: 28 June 2016
-#
-#@ 3676060800
-#
-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
-#
-# 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 3d037453 3acade76 570bd8f8 be2b8bc9 55ec6fe8
+# 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 rotatiob since the later
+# undergoes a full range of geophysical perturbations at various time scales (lunisolar
+# and core-mantle torques,atmospheric and oceanic effetcs, ...)
+# Leap seconds are needed to keep the two time scales in agreement, i.e. UT1-UTC smaller
+# than 0.9 second. So, when necessary a "leap second" is introduced in UTC.
+# Since the adoption of this system in 1972 it has been necessary to add 26 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 2000, it was necessary in average to add a leap second at a rate
+# of 1 to 2 years. Since 2000, due to the fact that the earth rate of rotation is accelerating, leap seconds are introduced
+# with an average frequency of 3 to 4 years.
+#
+#
+# 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 second date have to occur at fixed date :
+# first preference is given to the end of December and June, and second preference at the end of March
+# and September. Since the system was introduced in 1972, only dates in June and December were used.
+#
+# Questions or comments to:
+# Daniel Gambis, daniel.gambis at obspm.fr
+# Christian Bizouard: christian.bizouard at obspm.fr
+# Earth orientation Center of the IERS
+# Paris Observatory, France
+#
+#
+#
+# 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 (ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat)
+#
+# The following line shows the last update of this file in NTP timestamp:
+#
+#$ 3661632000
+#
+# 2) Expiration date of the file given on a semi-annual basis: last June or last December
+#
+# File expires on 28 December 2016
+#
+# Expire date in NTP timestamp:
+#
+#@ 3691872000
+#
+#
+# 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
+#
+# In order to verify the integrity of this file, a hash code
+# has been generated. For more information how to use
+# this hash code, please consult the README file under the
+# 'sha' repertory.
+#
+#h 99d52bb2 1cdd674e f9ec20e7 97d5d11e fe794939
--
2.7.0
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