2 # The Coordinated Universal Time (UTC) is the reference time scale derived
3 # from The "Temps Atomique International" (TAI) calculated by the Bureau
4 # International des Poids et Mesures (BIPM) using a worldwide network of atomic
5 # clocks. UTC differs from TAI by an integer number of seconds; it is the basis
6 # of all activities in the world.
9 # ASTRONOMICAL TIME (UT1) is the time scale based on the rate of rotation of the earth.
10 # It is now mainly derived from Very Long Baseline Interferometry (VLBI). The various
11 # irregular fluctuations progressively detected in the rotation rate of the Earth lead
12 # in 1972 to the replacement of UT1 by UTC as the reference time scale.
16 # Atomic clocks are more stable than the rate of the earth rotation since the latter
17 # undergoes a full range of geophysical perturbations at various time scales: lunisolar
18 # and core-mantle torques, atmospheric and oceanic effetcs, etc.
19 # Leap seconds are needed to keep the two time scales in agreement, i.e. UT1-UTC smaller
20 # than 0.9 second. Therefore, when necessary a "leap second" is applied to UTC.
21 # Since the adoption of this system in 1972 it has been necessary to add a number of seconds to UTC,
22 # firstly due to the initial choice of the value of the second (1/86400 mean solar day of
23 # the year 1820) and secondly to the general slowing down of the Earth's rotation. It is
24 # theorically possible to have a negative leap second (a second removed from UTC), but so far,
25 # all leap seconds have been positive (a second has been added to UTC). Based on what we know about
26 # the earth's rotation, it is unlikely that we will ever have a negative leap second.
30 # The first leap second was added on June 30, 1972. Until yhe year 2000, it was necessary in average to add a
31 # leap second at a rate of 1 to 2 years. Since the year 2000 leap seconds are introduced with an
32 # average interval of 3 to 4 years due to the acceleration of the Earth rotation speed.
35 # RESPONSABILITY OF THE DECISION TO INTRODUCE A LEAP SECOND IN UTC
36 # The decision to introduce a leap second in UTC is the responsibility of the Earth Orientation Center of
37 # the International Earth Rotation and reference System Service (IERS). This center is located at Paris
38 # Observatory. According to international agreements, leap seconds should only be scheduled for certain dates:
39 # first preference is given to the end of December and June, and second preference at the end of March
40 # and September. Since the introduction of leap seconds in 1972, only dates in June and December were used.
42 # Questions or comments to:
43 # Christian Bizouard: christian.bizouard@obspm.fr
44 # Earth orientation Center of the IERS
45 # Paris Observatory, France
49 # COPYRIGHT STATUS OF THIS FILE
50 # This file is in the public domain.
53 # VALIDITY OF THE FILE
54 # It is important to express the validity of the file. These next two dates are
55 # given in units of seconds since 1900.0.
57 # 1) Last update of the file.
59 # Updated through IERS Bulletin C (https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat)
61 # The following line shows the last update of this file in NTP timestamp:
65 # 2) Expiration date of the file given on a semi-annual basis: last June or last December
67 # File expires on 28 December 2024
69 # Expire date in NTP timestamp:
74 # LIST OF LEAP SECONDS
75 # NTP timestamp (X parameter) is the number of seconds since 1900.0
77 # MJD: The Modified Julian Day number. MJD = X/86400 + 15020
79 # DTAI: The difference DTAI= TAI-UTC in units of seconds
80 # It is the quantity to add to UTC to get the time in TAI
82 # Day Month Year : epoch in clear
84 #NTP Time DTAI Day Month Year
86 2272060800 10 # 1 Jan 1972
87 2287785600 11 # 1 Jul 1972
88 2303683200 12 # 1 Jan 1973
89 2335219200 13 # 1 Jan 1974
90 2366755200 14 # 1 Jan 1975
91 2398291200 15 # 1 Jan 1976
92 2429913600 16 # 1 Jan 1977
93 2461449600 17 # 1 Jan 1978
94 2492985600 18 # 1 Jan 1979
95 2524521600 19 # 1 Jan 1980
96 2571782400 20 # 1 Jul 1981
97 2603318400 21 # 1 Jul 1982
98 2634854400 22 # 1 Jul 1983
99 2698012800 23 # 1 Jul 1985
100 2776982400 24 # 1 Jan 1988
101 2840140800 25 # 1 Jan 1990
102 2871676800 26 # 1 Jan 1991
103 2918937600 27 # 1 Jul 1992
104 2950473600 28 # 1 Jul 1993
105 2982009600 29 # 1 Jul 1994
106 3029443200 30 # 1 Jan 1996
107 3076704000 31 # 1 Jul 1997
108 3124137600 32 # 1 Jan 1999
109 3345062400 33 # 1 Jan 2006
110 3439756800 34 # 1 Jan 2009
111 3550089600 35 # 1 Jul 2012
112 3644697600 36 # 1 Jul 2015
113 3692217600 37 # 1 Jan 2017
115 # A hash code has been generated to be able to verify the integrity
116 # of this file. For more information about using this hash code,
117 # please see the readme file in the 'source' directory :
118 # https://hpiers.obspm.fr/iers/bul/bulc/ntp/sources/README
120 #h 9dac5845 8acd32c0 2947d462 daf4a943 f58d9391