leapseconds revision 149514
1149514Swollman# @(#)leapseconds 7.20 275267Swollman 32742Swollman# Allowance for leapseconds added to each timezone file. 42742Swollman 52742Swollman# The International Earth Rotation Service periodically uses leap seconds 658787Sru# to keep UTC to within 0.9 s of UT1 758787Sru# (which measures the true angular orientation of the earth in space); see 82742Swollman# Terry J Quinn, The BIPM and the accurate measure of time, 92742Swollman# Proc IEEE 79, 7 (July 1991), 894-905. 102742Swollman# There were no leap seconds before 1972, because the official mechanism 112742Swollman# accounting for the discrepancy between atomic time and the earth's rotation 122742Swollman# did not exist until the early 1970s. 132742Swollman 142742Swollman# The correction (+ or -) is made at the given time, so lines 152742Swollman# will typically look like: 162742Swollman# Leap YEAR MON DAY 23:59:60 + R/S 172742Swollman# or 182742Swollman# Leap YEAR MON DAY 23:59:59 - R/S 192742Swollman 202742Swollman# If the leapsecond is Rolling (R) the given time is local time 2143014Swollman# If the leapsecond is Stationary (S) the given time is UTC 222742Swollman 232742Swollman# Leap YEAR MONTH DAY HH:MM:SS CORR R/S 242742SwollmanLeap 1972 Jun 30 23:59:60 + S 252742SwollmanLeap 1972 Dec 31 23:59:60 + S 262742SwollmanLeap 1973 Dec 31 23:59:60 + S 272742SwollmanLeap 1974 Dec 31 23:59:60 + S 282742SwollmanLeap 1975 Dec 31 23:59:60 + S 292742SwollmanLeap 1976 Dec 31 23:59:60 + S 302742SwollmanLeap 1977 Dec 31 23:59:60 + S 312742SwollmanLeap 1978 Dec 31 23:59:60 + S 322742SwollmanLeap 1979 Dec 31 23:59:60 + S 332742SwollmanLeap 1981 Jun 30 23:59:60 + S 342742SwollmanLeap 1982 Jun 30 23:59:60 + S 352742SwollmanLeap 1983 Jun 30 23:59:60 + S 362742SwollmanLeap 1985 Jun 30 23:59:60 + S 372742SwollmanLeap 1987 Dec 31 23:59:60 + S 382742SwollmanLeap 1989 Dec 31 23:59:60 + S 392742SwollmanLeap 1990 Dec 31 23:59:60 + S 402742SwollmanLeap 1992 Jun 30 23:59:60 + S 412742SwollmanLeap 1993 Jun 30 23:59:60 + S 422742SwollmanLeap 1994 Jun 30 23:59:60 + S 4339871SphkLeap 1995 Dec 31 23:59:60 + S 4439871SphkLeap 1997 Jun 30 23:59:60 + S 4539898SphkLeap 1998 Dec 31 23:59:60 + S 46147771SphkLeap 2005 Dec 31 23:59:60 + S 4786222Swollman 48149514Swollman# INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) 49149514Swollman# 50136638Swollman# SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE 51149514Swollman# 5275267Swollman# SERVICE DE LA ROTATION TERRESTRE 53149514Swollman# OBSERVATOIRE DE PARIS 5475267Swollman# 61, Av. de l'Observatoire 75014 PARIS (France) 5575267Swollman# Tel. : 33 (0) 1 40 51 22 26 5675267Swollman# FAX : 33 (0) 1 40 51 22 91 57149514Swollman# ... 58147771Sphk# http://hpiers.obspm.fr/eop-pc 59149514Swollman# 60149514Swollman# Paris, 4 July 2005 61149514Swollman# 62149514Swollman# Bulletin C 30 63149514Swollman# 64149514Swollman# To authorities responsible 65149514Swollman# for the measurement and 66149514Swollman# distribution of time 67149514Swollman# 68149514Swollman# 69147771Sphk# UTC TIME STEP 70147771Sphk# on the 1st of January 2006 71149514Swollman# 72149514Swollman# A positive leap second will be introduced at the end of December 2005. 73149514Swollman# The sequence of dates of the UTC second markers will be: 74149514Swollman# 75149514Swollman# 2005 December 31, 23h 59m 59s 76149514Swollman# 2005 December 31, 23h 59m 60s 77149514Swollman# 2006 January 1, 0h 0m 0s 78149514Swollman# 79149514Swollman# The difference between UTC and the International Atomic Time TAI is: 80149514Swollman# 81149514Swollman# from 1999 January 1, 0h UTC, to 2006 January 1 0h UTC : UTC-TAI = - 32s 82149514Swollman# from 2006 January 1, 0h UTC, until further notice : UTC-TAI = - 33s 83149514Swollman# 84149514Swollman# Leap seconds can be introduced in UtC at the end of the months of December 85149514Swollman# or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every 86149514Swollman# six months, either to announce a time step in UTC or to confirm that there 87149514Swollman# will be no time step at the next possible date. 88149514Swollman# 89149514Swollman# Daniel GAMBIS 90149514Swollman# Head 91149514Swollman# Earth Orientation Center of IERS 92149514Swollman# Observatoire de Paris, France 93