leapseconds.awk revision 309568 
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 available from most NIST time servers."
12  print "# If the URL <ftp://time.nist.gov/pub/leap-seconds.list> does not work,"
13  print "# you should be able to pick up leap-seconds.list from a secondary NIST server."
14  print "# See <http://tf.nist.gov/tf-cgi/servers.cgi> for a list of secondary servers."
15  print "# For more about leap-seconds.list, please see"
16  print "# The NTP Timescale and Leap Seconds"
17  print "# http://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); see"
22  print "# Terry J Quinn, The BIPM and the accurate measure of time,"
23  print "# Proc IEEE 79, 7 (July 1991), 894-905 <http://dx.doi.org/10.1109/5.84965>."
24  print "# There were no leap seconds before 1972, because the official mechanism"
25  print "# accounting for the discrepancy between atomic time and the earth's rotation"
26  print "# did not exist until the early 1970s."
27  print ""
28  print "# The correction (+ or -) is made at the given time, so lines"
29  print "# will typically look like:"
30  print "#	Leap	YEAR	MON	DAY	23:59:60	+	R/S"
31  print "# or"
32  print "#	Leap	YEAR	MON	DAY	23:59:59	-	R/S"
33  print ""
34  print "# If the leapsecond is Rolling (R) the given time is local time."
35  print "# If the leapsecond is Stationary (S) the given time is UTC."
36  print ""
37  print "# Leap	YEAR	MONTH	DAY	HH:MM:SS	CORR	R/S"
38}
39
40/^ *$/ { next }
41
42/^#\tUpdated through/ || /^#\tFile expires on:/ {
43    last_lines = last_lines $0 "\n"
44}
45
46/^#/ { next }
47
48{
49    NTP_timestamp = $1
50    TAI_minus_UTC = $2
51    hash_mark = $3
52    one = $4
53    month = $5
54    year = $6
55    if (old_TAI_minus_UTC) {
56	if (old_TAI_minus_UTC < TAI_minus_UTC) {
57	    sign = "23:59:60\t+"
58	} else {
59	    sign = "23:59:59\t-"
60	}
61	if (month == "Jan") {
62	    year--;
63	    month = "Dec";
64	    day = 31
65	} else if (month == "Jul") {
66	    month = "Jun";
67	    day = 30
68	}
69	printf "Leap\t%s\t%s\t%s\t%s\tS\n", year, month, day, sign
70    }
71    old_TAI_minus_UTC = TAI_minus_UTC
72}
73
74END {
75    printf "\n%s", last_lines
76}
77