leapseconds revision 169811
1169811Swollman# @(#)leapseconds 8.3 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 48169811Swollman# ... 49169811Swollman# Sent: Thursday, February 01, 2007 9:49 AM 50169811Swollman# ... 51169811Swollman# Subject: Bulletin C number 33 52149514Swollman# 53169811Swollman# INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) 54169811Swollman# 55136638Swollman# SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE 56149514Swollman# 5775267Swollman# SERVICE DE LA ROTATION TERRESTRE 58149514Swollman# OBSERVATOIRE DE PARIS 5975267Swollman# 61, Av. de l'Observatoire 75014 PARIS (France) 60169811Swollman# ... 61149514Swollman# 62169811Swollman# Paris, 1 February 2007 63169811Swollman# Bulletin C 33 64169811Swollman# To authorities responsible 65169811Swollman# for the measurement and 66169811Swollman# distribution of time 67149514Swollman# 68169811Swollman# INFORMATION ON UTC - TAI 69149514Swollman# 70169811Swollman# NO positive leap second will be introduced at the end of June 2007. 71169811Swollman# The difference between Coordinated Universal Time UTC and the 72169811Swollman# International Atomic Time TAI is: 73166422Sphk# from 2006 January 1, 0h UTC, until further notice : UTC-TAI = -33 s 74169811Swollman# Leap seconds can be introduced in UTC at the end of the months of 75169811Swollman# December or June, depending on the evolution of UT1-TAI. Bulletin C is 76169811Swollman# mailed every six months, either to announce a time step in UTC, or to 77169811Swollman# confirm that there will be no time step at the next possible date. 78166422Sphk# 79169811Swollman# Daniel GAMBIS 80169811Swollman# Director 81169811Swollman# Earth Orientation Center of IERS 82169811Swollman# Observatoire de Paris, France 83