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DOUBLE PRECISION FUNCTION sla_DAT (UTC)
*+
* - - - -
* D A T
* - - - -
*
* Increment to be applied to Coordinated Universal Time UTC to give
* International Atomic Time TAI (double precision)
*
* Given:
* UTC d UTC date as a modified JD (JD-2400000.5)
*
* Result: TAI-UTC in seconds
*
* Notes:
*
* 1 The UTC is specified to be a date rather than a time to indicate
* that care needs to be taken not to specify an instant which lies
* within a leap second. Though in most cases UTC can include the
* fractional part, correct behaviour on the day of a leap second
* can only be guaranteed up to the end of the second 23:59:59.
*
* 2 For epochs from 1961 January 1 onwards, the expressions from the
* file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used.
*
* 3 The 5ms timestep at 1961 January 1 is taken from 2.58.1 (p87) of
* the 1992 Explanatory Supplement.
*
* 4 UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper
* to call the routine with an earlier epoch. However, if this
* is attempted, the TAI-UTC expression for the year 1960 is used.
*
*
* :-----------------------------------------:
* : :
* : IMPORTANT :
* : :
* : This routine must be updated on each :
* : occasion that a leap second is :
* : announced :
* : :
* : Latest leap second: 1999 January 1 :
* : :
* :-----------------------------------------:
*
* P.T.Wallace Starlink 31 May 1999
*
* Copyright (C) 1999 Rutherford Appleton Laboratory
*-
IMPLICIT NONE
DOUBLE PRECISION UTC
DOUBLE PRECISION DT
IF (.FALSE.) THEN
* - - - - - - - - - - - - - - - - - - - - - - *
* Add new code here on each occasion that a *
* leap second is announced, and update the *
* preamble comments appropriately. *
* - - - - - - - - - - - - - - - - - - - - - - *
* 1999 January 1
ELSE IF (UTC.GE.51179D0) THEN
DT=32D0
* 1997 July 1
ELSE IF (UTC.GE.50630D0) THEN
DT=31D0
* 1996 January 1
ELSE IF (UTC.GE.50083D0) THEN
DT=30D0
* 1994 July 1
ELSE IF (UTC.GE.49534D0) THEN
DT=29D0
* 1993 July 1
ELSE IF (UTC.GE.49169D0) THEN
DT=28D0
* 1992 July 1
ELSE IF (UTC.GE.48804D0) THEN
DT=27D0
* 1991 January 1
ELSE IF (UTC.GE.48257D0) THEN
DT=26D0
* 1990 January 1
ELSE IF (UTC.GE.47892D0) THEN
DT=25D0
* 1988 January 1
ELSE IF (UTC.GE.47161D0) THEN
DT=24D0
* 1985 July 1
ELSE IF (UTC.GE.46247D0) THEN
DT=23D0
* 1983 July 1
ELSE IF (UTC.GE.45516D0) THEN
DT=22D0
* 1982 July 1
ELSE IF (UTC.GE.45151D0) THEN
DT=21D0
* 1981 July 1
ELSE IF (UTC.GE.44786D0) THEN
DT=20D0
* 1980 January 1
ELSE IF (UTC.GE.44239D0) THEN
DT=19D0
* 1979 January 1
ELSE IF (UTC.GE.43874D0) THEN
DT=18D0
* 1978 January 1
ELSE IF (UTC.GE.43509D0) THEN
DT=17D0
* 1977 January 1
ELSE IF (UTC.GE.43144D0) THEN
DT=16D0
* 1976 January 1
ELSE IF (UTC.GE.42778D0) THEN
DT=15D0
* 1975 January 1
ELSE IF (UTC.GE.42413D0) THEN
DT=14D0
* 1974 January 1
ELSE IF (UTC.GE.42048D0) THEN
DT=13D0
* 1973 January 1
ELSE IF (UTC.GE.41683D0) THEN
DT=12D0
* 1972 July 1
ELSE IF (UTC.GE.41499D0) THEN
DT=11D0
* 1972 January 1
ELSE IF (UTC.GE.41317D0) THEN
DT=10D0
* 1968 February 1
ELSE IF (UTC.GE.39887D0) THEN
DT=4.2131700D0+(UTC-39126D0)*0.002592D0
* 1966 January 1
ELSE IF (UTC.GE.39126D0) THEN
DT=4.3131700D0+(UTC-39126D0)*0.002592D0
* 1965 September 1
ELSE IF (UTC.GE.39004D0) THEN
DT=3.8401300D0+(UTC-38761D0)*0.001296D0
* 1965 July 1
ELSE IF (UTC.GE.38942D0) THEN
DT=3.7401300D0+(UTC-38761D0)*0.001296D0
* 1965 March 1
ELSE IF (UTC.GE.38820D0) THEN
DT=3.6401300D0+(UTC-38761D0)*0.001296D0
* 1965 January 1
ELSE IF (UTC.GE.38761D0) THEN
DT=3.5401300D0+(UTC-38761D0)*0.001296D0
* 1964 September 1
ELSE IF (UTC.GE.38639D0) THEN
DT=3.4401300D0+(UTC-38761D0)*0.001296D0
* 1964 April 1
ELSE IF (UTC.GE.38486D0) THEN
DT=3.3401300D0+(UTC-38761D0)*0.001296D0
* 1964 January 1
ELSE IF (UTC.GE.38395D0) THEN
DT=3.2401300D0+(UTC-38761D0)*0.001296D0
* 1963 November 1
ELSE IF (UTC.GE.38334D0) THEN
DT=1.9458580D0+(UTC-37665D0)*0.0011232D0
* 1962 January 1
ELSE IF (UTC.GE.37665D0) THEN
DT=1.8458580D0+(UTC-37665D0)*0.0011232D0
* 1961 August 1
ELSE IF (UTC.GE.37512D0) THEN
DT=1.3728180D0+(UTC-37300D0)*0.001296D0
* 1961 January 1
ELSE IF (UTC.GE.37300D0) THEN
DT=1.4228180D0+(UTC-37300D0)*0.001296D0
* Before that
ELSE
DT=1.4178180D0+(UTC-37300D0)*0.001296D0
END IF
sla_DAT=DT
END
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