SLA_DAT

TAI $-$ UTC

ACTION:: Increment to be applied to Coordinated Universal Time UTC to give International Atomic Time TAI.
CALL:: D = sla_DAT (UTC)

UTC	D	UTC date as a modified JD (JD $-$ 2400000.5)

sla_DAT	D	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 be guaranteed only up to the end of the second $2 3^{h} 5 9^{m} 5 9^{s}$ .
(2): For epochs from 1961 January 1 onwards, the expressions from the file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used. A 5ms time step at 1961 January 1 is taken from 2.58.1 (p87) of the 1992 Explanatory Supplement.
(3): 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.
(4): This routine has to be updated on each occasion that a leap second is announced, and programs using it relinked. Refer to the program source code for information on when the most recent leap second was added.