contrib/tzdata/leapseconds.awk

   1 # Generate the 'leapseconds' file from 'leap-seconds.list'.
   2
   3 # This file is in the public domain.
   4
   5 BEGIN {
   6   print "# Allowance for leap seconds added to each time zone file."
   7   print ""
   8   print "# This file is in the public domain."
   9   print ""
  10   print "# This file is generated automatically from the data in the public-domain"
  11   print "# leap-seconds.list file, which is copied from:"
  12   print "# ftp://ftp.nist.gov/pub/time/leap-seconds.list"
  13   print "# For more about leap-seconds.list, please see"
  14   print "# The NTP Timescale and Leap Seconds"
  15   print "# https://www.eecis.udel.edu/~mills/leap.html"
  16   print ""
  17   print "# The International Earth Rotation and Reference Systems Service"
  18   print "# periodically uses leap seconds to keep UTC to within 0.9 s of UT1"
  19   print "# (which measures the true angular orientation of the earth in space); see"
  20   print "# Levine J. Coordinated Universal Time and the leap second."
  21   print "# URSI Radio Sci Bull. 2016;89(4):30-6. doi:10.23919/URSIRSB.2016.7909995"
  22   print "# http://ieeexplore.ieee.org/document/7909995/"
  23   print "# There were no leap seconds before 1972, because the official mechanism"
  24   print "# accounting for the discrepancy between atomic time and the earth's rotation"
  25   print "# did not exist until the early 1970s."
  26   print ""
  27   print "# The correction (+ or -) is made at the given time, so lines"
  28   print "# will typically look like:"
  29   print "#      Leap    YEAR    MON     DAY     23:59:60        +       R/S"
  30   print "# or"
  31   print "#      Leap    YEAR    MON     DAY     23:59:59        -       R/S"
  32   print ""
  33   print "# If the leapsecond is Rolling (R) the given time is local time."
  34   print "# If the leapsecond is Stationary (S) the given time is UTC."
  35   print ""
  36   print "# Leap YEAR    MONTH   DAY     HH:MM:SS        CORR    R/S"
  37 }
  38
  39 /^ *$/ { next }
  40
  41 /^#\tUpdated through/ || /^#\tFile expires on:/ {
  42     last_lines = last_lines $0 "\n"
  43 }
  44
  45 /^#/ { next }
  46
  47 {
  48     NTP_timestamp = $1
  49     TAI_minus_UTC = $2
  50     hash_mark = $3
  51     one = $4
  52     month = $5
  53     year = $6
  54     if (old_TAI_minus_UTC) {
  55         if (old_TAI_minus_UTC < TAI_minus_UTC) {
  56             sign = "23:59:60\t+"
  57         } else {
  58             sign = "23:59:59\t-"
  59         }
  60         if (month == "Jan") {
  61             year--;
  62             month = "Dec";
  63             day = 31
  64         } else if (month == "Jul") {
  65             month = "Jun";
  66             day = 30
  67         }
  68         printf "Leap\t%s\t%s\t%s\t%s\tS\n", year, month, day, sign
  69     }
  70     old_TAI_minus_UTC = TAI_minus_UTC
  71 }
  72
  73 END {
  74     printf "\n%s", last_lines
  75 }