Increment to be applied to Coordinated Universal Time UTC to give Terrestrial Time TT (formerly Ephemeris Time ET). (double precision)
utc double UTC date as a modified JD (JD-2400000.5) Result: TT-UTC in seconds Pre 1972 January 1 a fixed value of 10 + ET-TAI is returned.
slaDat P.T.Wallace Starlink 31 October 1993