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# Generate the 'leapseconds' file from 'leap-seconds.list'.
# This file is in the public domain.
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 "# <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 "# 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 "# 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 "# 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 "# 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."
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)."
monthabbr[ 1] = "Jan"
monthabbr[ 2] = "Feb"
monthabbr[ 3] = "Mar"
monthabbr[ 4] = "Apr"
monthabbr[ 5] = "May"
monthabbr[ 6] = "Jun"
monthabbr[ 7] = "Jul"
monthabbr[ 8] = "Aug"
monthabbr[ 9] = "Sep"
monthabbr[10] = "Oct"
monthabbr[11] = "Nov"
monthabbr[12] = "Dec"
for (i in monthabbr) {
monthnum[monthabbr[i]] = i
monthlen[i] = 31
}
monthlen[2] = 28
monthlen[4] = monthlen[6] = monthlen[9] = monthlen[11] = 30
}
/^#\tUpdated through/ || /^#\tFile expires on:/ {
last_lines = last_lines $0 "\n"
}
/^#[$][ \t]/ { updated = $2 }
/^#[@][ \t]/ { expires = $2 }
/^#/ { 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
}
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
}
END {
# The difference between the NTP and POSIX epochs is 70 years
# (including 17 leap days), each 24 hours of 60 minutes of 60
# seconds each.
epoch_minus_NTP = ((1970 - 1900) * 365 + 17) * 24 * 60 * 60
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
printf "\n%s", last_lines
}
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