On Tue, Aug 13, 2013 at 3:07 AM, Paul Eggert <eggert@cs.ucla.edu> wrote:

Bradley White privately sent a Perl script to generate
'leapseconds' from the NIST leap-seconds.list file.
Since we use POSIX Awk for the other processing
it's probably better to use Awk here, too, so here's a proposed
patch with all the Makefile bells and whistles, which I pushed
to the experimental github repository. The patch removes the
file 'leapseconds' from the repository because it's now generated
automatically. I took the liberty of removing the copy of the
IERS announcement from the generated 'leapseconds' since its copyright
status was unclear. The NIST leap-seconds.list file is public domain,
so it's OK for us to redistribute it.

>From 459b72d3edec98488e5132d4473c4678b4ed5a73 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 12 Aug 2013 23:58:29 -0700
Subject: [PATCH] Generate the 'leapseconds' file automatically from
leap-seconds.list.

* leap-seconds.list: New file, copied from the NIST.
* leapseconds: Remove from git; it's now generated.
* leapseconds.awk: New file.
* Makefile (DATA): Add leap-seconds.list. Remove leapseconds.
(MISC): Add leapseconds.awk.
(leapseconds): New rule.
(right_posix, posix_right): Depend on leapseconds.
(clean_misc): Remove leapseconds.
---
Makefile | 14 ++--
leap-seconds.list | 231 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
leapseconds | 100 -----------------------
leapseconds.awk | 68 ++++++++++++++++
4 files changed, 308 insertions(+), 105 deletions(-)
create mode 100644 leap-seconds.list
delete mode 100644 leapseconds
create mode 100644 leapseconds.awk

diff --git a/Makefile b/Makefile
index db7f56e..68d7132 100644
--- a/Makefile
+++ b/Makefile
@@ -318,10 +318,11 @@ NDATA= systemv factory
SDATA= solar87 solar88 solar89
TDATA= $(YDATA) $(NDATA) $(SDATA)
TABDATA= iso3166.tab zone.tab
-DATA= $(YDATA) $(NDATA) $(SDATA) $(TABDATA) leapseconds yearistype.sh
+DATA= $(YDATA) $(NDATA) $(SDATA) $(TABDATA) \
+ leap-seconds.list yearistype.sh
WEB_PAGES= tz-art.htm tz-link.htm
MISC= usno1988 usno1989 usno1989a usno1995 usno1997 usno1998 \
- $(WEB_PAGES) checktab.awk workman.sh \
+ $(WEB_PAGES) checktab.awk leapseconds.awk workman.sh \
zoneinfo2tdf.pl
ENCHILADA= $(COMMON) $(DOCS) $(SOURCES) $(DATA) $(MISC)

@@ -375,6 +376,9 @@ yearistype: yearistype.sh
cp yearistype.sh yearistype
chmod +x yearistype

+leapseconds: leapseconds.awk leap-seconds.list
+ $(AWK) -f leapseconds.awk leap-seconds.list >$@
+
posix_only: zic $(TDATA)
$(ZIC) -y $(YEARISTYPE) -d $(TZDIR) -L /dev/null $(TDATA)

@@ -390,14 +394,14 @@ right_only: zic leapseconds $(TDATA)
# Therefore, the other two directories are now siblings of $(TZDIR).
# You must replace all of $(TZDIR) to switch from not using leap seconds
# to using them, or vice versa.
-right_posix: right_only
+right_posix: right_only leapseconds
rm -fr $(TZDIR)-leaps
ln -s $(TZDIR_BASENAME) $(TZDIR)-leaps || \
$(ZIC) -y $(YEARISTYPE) \
-d $(TZDIR)-leaps -L leapseconds $(TDATA)
$(ZIC) -y $(YEARISTYPE) -d $(TZDIR)-posix -L /dev/null $(TDATA)

-posix_right: posix_only
+posix_right: posix_only leapseconds
rm -fr $(TZDIR)-posix
ln -s $(TZDIR_BASENAME) $(TZDIR)-posix || \
$(ZIC) -y $(YEARISTYPE) \
@@ -440,7 +444,7 @@ check_web: $(WEB_PAGES)

clean_misc:
rm -f core *.o *.out \
- date tzselect version.h zdump zic yearistype
+ date leapseconds tzselect version.h zdump zic yearistype
clean: clean_misc
rm -f -r tzpublic

diff --git a/leap-seconds.list b/leap-seconds.list
new file mode 100644
index 0000000..7df3de6
--- /dev/null
+++ b/leap-seconds.list
@@ -0,0 +1,231 @@
+#
+# 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 1900.0 and 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.fr for more information.
+#
+# 3. The current defintion of the relationship between UTC
+# and TAI dates from 1 January 1972. A number of different
+# time scales were in use before than 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 insertion of leap seconds into UTC is currently the
+# responsibility of the International Earth Rotation Service,
+# which is located at the Paris Observatory:
+#
+# Central Bureau of IERS
+# 61, Avenue de l'Observatoire
+# 75014 Paris, France.
+#
+# Leap seconds are announced by the IERS in its Bulletin C
+#
+# See hpiers.obspm.fr or www.iers.org for more details.
+#
+# All national laboratories and timing centers use the
+# data from the BIPM and the IERS to construct their
+# local realizations 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 equivlent 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.
+#
+# 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.
+#
+# Questions or comments to:
+# Judah Levine
+# Time and Frequency Division
+# NIST
+# Boulder, Colorado
+# jlevine@boulder.nist.gov
+#
+# Last Update of leap second values: 11 January 2012
+#
+# 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.
+#
+#$ 3535228800
+#
+# The NTP timestamps are in units of seconds since the NTP epoch,
+# which is 1900.0. 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 1900.0. 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 1900.0. 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 C46
+# File expires on: 28 June 2014
+#
+#@ 3612902400
+#
+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
+#
+# 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 1151a8f e85a5069 9000fcdb 3d5e5365 1d505b37
diff --git a/leapseconds b/leapseconds
deleted file mode 100644
index 5b5c70e..0000000
--- a/leapseconds
+++ /dev/null
@@ -1,100 +0,0 @@
-# <pre>
-# This file is in the public domain, so clarified as of
-# 2009-05-17 by Arthur David Olson.
-
-# Allowance for leapseconds added to each timezone file.
-
-# The International Earth Rotation Service periodically uses leap seconds
-# to keep UTC to within 0.9 s of UT1
-# (which measures the true angular orientation of the earth in space); see
-# Terry J Quinn, The BIPM and the accurate measure of time,
-# Proc IEEE 79, 7 (July 1991), 894-905.
-# There were no leap seconds before 1972, because the official mechanism
-# accounting for the discrepancy between atomic time and the earth's rotation
-# did not exist until the early 1970s.
-
-# The correction (+ or -) is made at the given time, so lines
-# will typically look like:
-# Leap YEAR MON DAY 23:59:60 + R/S
-# or
-# Leap YEAR MON DAY 23:59:59 - R/S
-
-# If the leapsecond is Rolling (R) the given time is local time
-# If the leapsecond is Stationary (S) the given time is UTC
-
-# Leap YEAR MONTH DAY HH:MM:SS CORR R/S
-Leap 1972 Jun 30 23:59:60 + S
-Leap 1972 Dec 31 23:59:60 + S
-Leap 1973 Dec 31 23:59:60 + S
-Leap 1974 Dec 31 23:59:60 + S
-Leap 1975 Dec 31 23:59:60 + S
-Leap 1976 Dec 31 23:59:60 + S
-Leap 1977 Dec 31 23:59:60 + S
-Leap 1978 Dec 31 23:59:60 + S
-Leap 1979 Dec 31 23:59:60 + S
-Leap 1981 Jun 30 23:59:60 + S
-Leap 1982 Jun 30 23:59:60 + S
-Leap 1983 Jun 30 23:59:60 + S
-Leap 1985 Jun 30 23:59:60 + S
-Leap 1987 Dec 31 23:59:60 + S
-Leap 1989 Dec 31 23:59:60 + S
-Leap 1990 Dec 31 23:59:60 + S
-Leap 1992 Jun 30 23:59:60 + S
-Leap 1993 Jun 30 23:59:60 + S
-Leap 1994 Jun 30 23:59:60 + S
-Leap 1995 Dec 31 23:59:60 + S
-Leap 1997 Jun 30 23:59:60 + S
-Leap 1998 Dec 31 23:59:60 + S
-Leap 2005 Dec 31 23:59:60 + S
-Leap 2008 Dec 31 23:59:60 + S
-Leap 2012 Jun 30 23:59:60 + S
-
-# INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)
-#
-# SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE
-#
-#
-# SERVICE DE LA ROTATION TERRESTRE
-# OBSERVATOIRE DE PARIS
-# 61, Av. de l'Observatoire 75014 PARIS (France)
-# Tel. : 33 (0) 1 40 51 22 26
-# FAX : 33 (0) 1 40 51 22 91
-# e-mail : (E-Mail Removed)
-# http://hpiers.obspm.fr/eop-pc
-#
-# Paris, 5 January 2012
-#
-#
-# Bulletin C 43
-#
-# To authorities responsible
-# for the measurement and
-# distribution of time
-#
-#
-# UTC TIME STEP
-# on the 1st of July 2012
-#
-#
-# A positive leap second will be introduced at the end of June 2012.
-# The sequence of dates of the UTC second markers will be:
-#
-# 2012 June 30, 23h 59m 59s
-# 2012 June 30, 23h 59m 60s
-# 2012 July 1, 0h 0m 0s
-#
-# The difference between UTC and the International Atomic Time TAI is:
-#
-# from 2009 January 1, 0h UTC, to 2012 July 1 0h UTC : UTC-TAI = - 34s
-# from 2012 July 1, 0h UTC, until further notice : UTC-TAI = - 35s
-#
-# Leap seconds can be introduced in UTC at the end of the months of December
-# or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every
-# six months, either to announce a time step in UTC or to confirm that there
-# will be no time step at the next possible date.
-#
-#
-# Daniel GAMBIS
-# Head
-# Earth Orientation Center of IERS
-# Observatoire de Paris, France
diff --git a/leapseconds.awk b/leapseconds.awk
new file mode 100644
index 0000000..732db99
--- /dev/null
+++ b/leapseconds.awk
@@ -0,0 +1,68 @@
+# Generate the 'leapseconds' file from 'leap-seconds.list'.
+
+# This file is in the public domain.
+
+BEGIN {
+ printf "%s", "\
+# Allowance for leapseconds added to each timezone file.\n\
+\n\
+# This file is in the public domain.\n\
+\n\
+# This file is generated automatically from the data in the public-domain\n\
+# leap-seconds.list file available from most NIST time servers.\n\
+# If the URL <ftp://time.nist.gov/pub/leap-seconds.list> does not work,\n\
+# you should be able to pick up leap-seconds.list from a secondary NIST server.\n\
+# For more about leap-seconds.list, please see\n\
+# The NTP Timescale and Leap Seconds\n\
+# <http://www.eecis.udel.edu/~mills/leap.html>.\n\
+\n\
+# The International Earth Rotation Service periodically uses leap seconds\n\
+# to keep UTC to within 0.9 s of UT1\n\
+# (which measures the true angular orientation of the earth in space); see\n\
+# Terry J Quinn, The BIPM and the accurate measure of time,\n\
+# Proc IEEE 79, 7 (July 1991), 894-905 <http://dx.doi.org/10.1109/5.84965>.\n\
+# There were no leap seconds before 1972, because the official mechanism\n\
+# accounting for the discrepancy between atomic time and the earth's rotation\n\
+# did not exist until the early 1970s.\n\
+\n\
+# The correction (+ or -) is made at the given time, so lines\n\
+# will typically look like:\n\
+# Leap YEAR MON DAY 23:59:60 + R/S\n\
+# or\n\
+# Leap YEAR MON DAY 23:59:59 - R/S\n\
+\n\
+# If the leapsecond is Rolling (R) the given time is local time.\n\
+# If the leapsecond is Stationary (S) the given time is UTC.\n\
+\n\
+# Leap YEAR MONTH DAY HH:MM:SS CORR R/S\n\
+"
+}
+
+/^ *$/ { next }
+/^#/ { next }
+
+{
+ NTP_timestamp = $1
+ TAI_minus_UTC = $2
+ hash_mark = $3
+ one = $4
+ month = $5
+ year = $6
+ if (old_TAI_minus_UTC) {
+ if (old_TAI_minus_UTC < TAI_minus_UTC) {
+ sign = "23:59:60\t+"
+ } else {
+ sign = "23:59:59\t-"
+ }
+ if (month == "Jan") {
+ year--;
+ month = "Dec";
+ day = 31
+ } else if (month == "Jul") {
+ month = "Jun";
+ day = 30
+ }
+ printf "Leap\t%s\t%s\t%s\t%s\tS\n", year, month, day, sign
+ }
+ old_TAI_minus_UTC = TAI_minus_UTC
+}
--
1.8.1.2