leapseconds.awk revision 325159 
1# Generate the 'leapseconds' file from 'leap-seconds.list'.
2
3# This file is in the public domain.
4
5BEGIN {
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
73END {
74    printf "\n%s", last_lines
75}
76