Unleashed v1.4
[unleashed.git] / contrib / tzdata / leapseconds.awk
blobea0567cd7f683f3b12d360088e047006c28e0f0e
1 # Generate the 'leapseconds' file from 'leap-seconds.list'.
3 # This file is in the public domain.
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 can be copied from"
12 print "# <ftp://ftp.nist.gov/pub/time/leap-seconds.list>"
13 print "# or <ftp://ftp.boulder.nist.gov/pub/time/leap-seconds.list>"
14 print "# or <ftp://tycho.usno.navy.mil/pub/ntp/leap-seconds.list>."
15 print "# For more about leap-seconds.list, please see"
16 print "# The NTP Timescale and Leap Seconds"
17 print "# <https://www.eecis.udel.edu/~mills/leap.html>."
18 print ""
19 print "# The International Earth Rotation and Reference Systems Service"
20 print "# periodically uses leap seconds to keep UTC to within 0.9 s of UT1"
21 print "# (which measures the true angular orientation of the earth in space)"
22 print "# and publishes leap second data in a copyrighted file"
23 print "# <https://hpiers.obspm.fr/iers/bul/bulc/Leap_Second.dat>."
24 print "# See: Levine J. Coordinated Universal Time and the leap second."
25 print "# URSI Radio Sci Bull. 2016;89(4):30-6. doi:10.23919/URSIRSB.2016.7909995"
26 print "# <https://ieeexplore.ieee.org/document/7909995>."
27 print "# There were no leap seconds before 1972, because the official mechanism"
28 print "# accounting for the discrepancy between atomic time and the earth's rotation"
29 print "# did not exist."
30 print ""
31 print "# The correction (+ or -) is made at the given time, so lines"
32 print "# will typically look like:"
33 print "# Leap YEAR MON DAY 23:59:60 + R/S"
34 print "# or"
35 print "# Leap YEAR MON DAY 23:59:59 - R/S"
36 print ""
37 print "# If the leap second is Rolling (R) the given time is local time (unused here)."
39 monthabbr[ 1] = "Jan"
40 monthabbr[ 2] = "Feb"
41 monthabbr[ 3] = "Mar"
42 monthabbr[ 4] = "Apr"
43 monthabbr[ 5] = "May"
44 monthabbr[ 6] = "Jun"
45 monthabbr[ 7] = "Jul"
46 monthabbr[ 8] = "Aug"
47 monthabbr[ 9] = "Sep"
48 monthabbr[10] = "Oct"
49 monthabbr[11] = "Nov"
50 monthabbr[12] = "Dec"
51 for (i in monthabbr) {
52 monthnum[monthabbr[i]] = i
53 monthlen[i] = 31
55 monthlen[2] = 28
56 monthlen[4] = monthlen[6] = monthlen[9] = monthlen[11] = 30
59 /^#\tUpdated through/ || /^#\tFile expires on:/ {
60 last_lines = last_lines $0 "\n"
63 /^#[$][ \t]/ { updated = $2 }
64 /^#[@][ \t]/ { expires = $2 }
66 /^#/ { next }
69 NTP_timestamp = $1
70 TAI_minus_UTC = $2
71 hash_mark = $3
72 one = $4
73 month = $5
74 year = $6
75 if (old_TAI_minus_UTC) {
76 if (old_TAI_minus_UTC < TAI_minus_UTC) {
77 sign = "23:59:60\t+"
78 } else {
79 sign = "23:59:59\t-"
81 m = monthnum[month] - 1
82 if (m == 0) {
83 year--;
84 m = 12
86 month = monthabbr[m]
87 day = monthlen[m]
88 day += m == 2 && year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)
89 printf "Leap\t%s\t%s\t%s\t%s\tS\n", year, month, day, sign
91 old_TAI_minus_UTC = TAI_minus_UTC
94 END {
95 # The difference between the NTP and POSIX epochs is 70 years
96 # (including 17 leap days), each 24 hours of 60 minutes of 60
97 # seconds each.
98 epoch_minus_NTP = ((1970 - 1900) * 365 + 17) * 24 * 60 * 60
100 print ""
101 print "# POSIX timestamps for the data in this file:"
102 printf "#updated %s\n", updated - epoch_minus_NTP
103 printf "#expires %s\n", expires - epoch_minus_NTP
104 printf "\n%s", last_lines