leapseconds revision 171948
1171948Sedwin# @(#)leapseconds 8.4 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 48171948Sedwin# INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) 49136638Swollman# SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE 50149514Swollman# 5175267Swollman# SERVICE DE LA ROTATION TERRESTRE 52149514Swollman# OBSERVATOIRE DE PARIS 5375267Swollman# 61, Av. de l'Observatoire 75014 PARIS (France) 54171948Sedwin# Tel. : 33 (0) 1 40 51 22 26 55171948Sedwin# FAX : 33 (0) 1 40 51 22 91 56171948Sedwin# Internet : services.iers@obspm.fr 57149514Swollman# 58171948Sedwin# Paris, 28 June 2007 59149514Swollman# 60171948Sedwin# Bulletin C 34 61149514Swollman# 62171948Sedwin# To authorities responsible 63171948Sedwin# for the measurement and 64171948Sedwin# distribution of time 65171948Sedwin# 66171948Sedwin# INFORMATION ON UTC - TAI 67171948Sedwin# 68171424Sphk# NO positive leap second will be introduced at the end of December 2007. 69169811Swollman# The difference between Coordinated Universal Time UTC and the 70171948Sedwin# International Atomic Time TAI is : 71166422Sphk# 72171948Sedwin# from 2006 January 1, 0h UTC, until further notice : UTC-TAI = -33 s 73171948Sedwin# 74171948Sedwin# Leap seconds can be introduced in UTC at the end of the months of December 75171948Sedwin# or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every 76171948Sedwin# six months, either to announce a time step in UTC, or to confirm that there 77171948Sedwin# will be no time step at the next possible date. 78171948Sedwin# 79171948Sedwin# Daniel GAMBIS 80171948Sedwin# Director 81171948Sedwin# Earth Orientation Center of IERS 82171948Sedwin# Observatoire de Paris, France 83