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2019-10-29

2019-10-29 10:12:27 by Henrik Grubbström (Grubba) <grubba@grubba.org>

Updated to tzdata2019c.

1: - # Generate the 'leapseconds' file from 'leap-seconds.list'. + # Generate zic format 'leapseconds' from NIST format 'leap-seconds.list'.      # This file is in the public domain.    -  + # This program uses awk arithmetic. POSIX requires awk to support + # exact integer arithmetic only through 10**10, which means for NTP + # timestamps this program works only to the year 2216, which is the + # year 1900 plus 10**10 seconds. However, in practice + # POSIX-conforming awk implementations invariably use IEEE-754 double + # and so support exact integers through 2**53. By the year 2216, + # POSIX will almost surely require at least 2**53 for awk, so for NTP + # timestamps this program should be good until the year 285,428,681 + # (the year 1900 plus 2**53 seconds). By then leap seconds will be + # long obsolete, as the Earth will likely slow down so much that + # there will be more than 25 hours per day and so some other scheme + # will be needed. +    BEGIN {    print "# Allowance for leap seconds added to each time zone file."    print ""    print "# This file is in the public domain."    print ""    print "# This file is generated automatically from the data in the public-domain" -  print "# leap-seconds.list file, which can be copied from" +  print "# NIST format leap-seconds.list file, which can be copied from"    print "# <ftp://ftp.nist.gov/pub/time/leap-seconds.list>" -  print "# or <ftp://ftp.boulder.nist.gov/pub/time/leap-seconds.list>" -  print "# or <ftp://tycho.usno.navy.mil/pub/ntp/leap-seconds.list>." +  print "# or <ftp://ftp.boulder.nist.gov/pub/time/leap-seconds.list>."    print "# For more about leap-seconds.list, please see"    print "# The NTP Timescale and Leap Seconds"    print "# <https://www.eecis.udel.edu/~mills/leap.html>."    print "" -  print "# The International Earth Rotation and Reference Systems Service" +  print "# The rules for leap seconds are specified in Annex 1 (Time scales) of:" +  print "# Standard-frequency and time-signal emissions." +  print "# International Telecommunication Union - Radiocommunication Sector" +  print "# (ITU-R) Recommendation TF.460-6 (02/2002)" +  print "# <https://www.itu.int/rec/R-REC-TF.460-6-200202-I/>." +  print "# The International Earth Rotation and Reference Systems Service (IERS)"    print "# periodically uses leap seconds to keep UTC to within 0.9 s of UT1" -  print "# (which measures the true angular orientation of the earth in space)" +  print "# (a proxy for Earth's angle in space as measured by astronomers)"    print "# and publishes leap second data in a copyrighted file"    print "# <https://hpiers.obspm.fr/iers/bul/bulc/Leap_Second.dat>."    print "# See: Levine J. Coordinated Universal Time and the leap second."    print "# URSI Radio Sci Bull. 2016;89(4):30-6. doi:10.23919/URSIRSB.2016.7909995"    print "# <https://ieeexplore.ieee.org/document/7909995>."    print "" -  print "# There were no leap seconds before 1972, because the official mechanism" -  print "# accounting for the discrepancy between atomic time and the earth's rotation" -  print "# did not exist. The first (\"1 Jan 1972\") data line in leap-seconds.list" +  print "# There were no leap seconds before 1972, as no official mechanism" +  print "# accounted for the discrepancy between atomic time (TAI) and the earth's" +  print "# rotation. The first (\"1 Jan 1972\") data line in leap-seconds.list"    print "# does not denote a leap second; it denotes the start of the current definition" -  print"# of UTC." +  print "# of UTC."    print "" -  print "# The correction (+ or -) is made at the given time, so lines" -  print "# will typically look like:" -  print "# Leap YEAR MON DAY 23:59:60 + R/S" -  print "# or" -  print "# Leap YEAR MON DAY 23:59:59 - R/S" -  print "" -  print "# If the leap second is Rolling (R) the given time is local time (unused here)." +  print "# All leap-seconds are Stationary (S) at the given UTC time." +  print "# The correction (+ or -) is made at the given time, so in the unlikely" +  print "# event of a negative leap second, a line would look like this:" +  print "# Leap YEAR MON DAY 23:59:59 - S" +  print "# Typical lines look like this:" +  print "# Leap YEAR MON DAY 23:59:60 + S"       monthabbr[ 1] = "Jan"    monthabbr[ 2] = "Feb"
51:    monthabbr[10] = "Oct"    monthabbr[11] = "Nov"    monthabbr[12] = "Dec" -  for (i in monthabbr) { -  monthnum[monthabbr[i]] = i -  monthlen[i] = 31 +  +  # Strip trailing CR, in case the input has CRLF form a la NIST. +  RS = "\r?\n" +  +  sstamp_init()   } -  monthlen[2] = 28 -  monthlen[4] = monthlen[6] = monthlen[9] = monthlen[11] = 30 - } +     - /^#\tUpdated through/ || /^#\tFile expires on:/ { + /^#[ \t]*[Uu]pdated through/ || /^#[ \t]*[Ff]ile expires on/ {    last_lines = last_lines $0 "\n"   }      /^#[$][ \t]/ { updated = $2 }   /^#[@][ \t]/ { expires = $2 }    - /^#/ { next } + /^[ \t]*#/ { 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-"    } -  m = monthnum[month] - 1 -  if (m == 0) { -  year--; -  m = 12 +  sstamp_to_ymdhMs(NTP_timestamp - 1, ss_NTP) +  printf "Leap\t%d\t%s\t%d\t%s\tS\n", \ +  ss_year, monthabbr[ss_month], ss_mday, sign    } -  month = monthabbr[m] -  day = monthlen[m] -  day += m == 2 && year % 4 == 0 && (year % 100 != 0 || year % 400 == 0) -  printf "Leap\t%s\t%s\t%s\t%s\tS\n", year, month, day, sign -  } +     old_TAI_minus_UTC = TAI_minus_UTC   }   
102:       print ""    print "# POSIX timestamps for the data in this file:" -  printf "#updated %s\n", updated - epoch_minus_NTP -  printf "#expires %s\n", expires - epoch_minus_NTP +  sstamp_to_ymdhMs(updated, ss_NTP) +  printf "#updated %d (%.4d-%.2d-%.2d %.2d:%.2d:%.2d UTC)\n", \ +  updated - epoch_minus_NTP, \ +  ss_year, ss_month, ss_mday, ss_hour, ss_min, ss_sec +  sstamp_to_ymdhMs(expires, ss_NTP) +  printf "#expires %d (%.4d-%.2d-%.2d %.2d:%.2d:%.2d UTC)\n", \ +  expires - epoch_minus_NTP, \ +  ss_year, ss_month, ss_mday, ss_hour, ss_min, ss_sec +     printf "\n%s", last_lines   } -  +  + # sstamp_to_ymdhMs - convert seconds timestamp to date and time + # + # Call as: + # + # sstamp_to_ymdhMs(sstamp, epoch_days) + # + # where: + # + # sstamp - is the seconds timestamp. + # epoch_days - is the timestamp epoch in Gregorian days since 1600-03-01. + # ss_NTP is appropriate for an NTP sstamp. + # + # Both arguments should be nonnegative integers. + # On return, the following variables are set based on sstamp: + # + # ss_year - Gregorian calendar year + # ss_month - month of the year (1-January to 12-December) + # ss_mday - day of the month (1-31) + # ss_hour - hour (0-23) + # ss_min - minute (0-59) + # ss_sec - second (0-59) + # ss_wday - day of week (0-Sunday to 6-Saturday) + # + # The function sstamp_init should be called prior to using sstamp_to_ymdhMs. +  + function sstamp_init() + { +  # Days in month N, where March is month 0 and January month 10. +  ss_mon_days[ 0] = 31 +  ss_mon_days[ 1] = 30 +  ss_mon_days[ 2] = 31 +  ss_mon_days[ 3] = 30 +  ss_mon_days[ 4] = 31 +  ss_mon_days[ 5] = 31 +  ss_mon_days[ 6] = 30 +  ss_mon_days[ 7] = 31 +  ss_mon_days[ 8] = 30 +  ss_mon_days[ 9] = 31 +  ss_mon_days[10] = 31 +  +  # Counts of days in a Gregorian year, quad-year, century, and quad-century. +  ss_year_days = 365 +  ss_quadyear_days = ss_year_days * 4 + 1 +  ss_century_days = ss_quadyear_days * 25 - 1 +  ss_quadcentury_days = ss_century_days * 4 + 1 +  +  # Standard day epochs, suitable for epoch_days. +  # ss_MJD = 94493 +  # ss_POSIX = 135080 +  ss_NTP = 109513 + } +  + function sstamp_to_ymdhMs(sstamp, epoch_days, \ +  quadcentury, century, quadyear, year, month, day) + { +  ss_hour = int(sstamp / 3600) % 24 +  ss_min = int(sstamp / 60) % 60 +  ss_sec = sstamp % 60 +  +  # Start with a count of days since 1600-03-01 Gregorian. +  day = epoch_days + int(sstamp / (24 * 60 * 60)) +  +  # Compute a year-month-day date with days of the month numbered +  # 0-30, months (March-February) numbered 0-11, and years that start +  # start March 1 and end after the last day of February. A quad-year +  # starts on March 1 of a year evenly divisible by 4 and ends after +  # the last day of February 4 years later. A century starts on and +  # ends before March 1 in years evenly divisible by 100. +  # A quad-century starts on and ends before March 1 in years divisible +  # by 400. While the number of days in a quad-century is a constant, +  # the number of days in each other time period can vary by 1. +  # Any variation is in the last day of the time period (there might +  # or might not be a February 29) where it is easy to deal with. +  +  quadcentury = int(day / ss_quadcentury_days) +  day -= quadcentury * ss_quadcentury_days +  ss_wday = (day + 3) % 7 +  century = int(day / ss_century_days) +  century -= century == 4 +  day -= century * ss_century_days +  quadyear = int(day / ss_quadyear_days) +  day -= quadyear * ss_quadyear_days +  year = int(day / ss_year_days) +  year -= year == 4 +  day -= year * ss_year_days +  for (month = 0; month < 11; month++) { +  if (day < ss_mon_days[month]) +  break +  day -= ss_mon_days[month] +  } +  +  # Convert the date to a conventional day of month (1-31), +  # month (1-12, January-December) and Gregorian year. +  ss_mday = day + 1 +  if (month <= 9) { +  ss_month = month + 3 +  } else { +  ss_month = month - 9 +  year++ +  } +  ss_year = 1600 + quadcentury * 400 + century * 100 + quadyear * 4 + year + }