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era.taiutc.md

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eraTaiutc

[rv, utc1, utc2] = ERFA.taiutc(tai1, tai2)

Time scale transformation: International Atomic Time, TAI, to Coordinated Universal Time, UTC.

Given:

   tai1,tai2  double   TAI as a 2-part Julian Date (Note 1)

Returned:

   utc1,utc2  double   UTC as a 2-part quasi Julian Date (Notes 1-3)

Returned (function value):

              int      status: +1 = dubious year (Note 4)
                                0 = OK
                               -1 = unacceptable date

Notes:

  1. tai1+tai2 is Julian Date, apportioned in any convenient way between the two arguments, for example where tai1 is the Julian Day Number and tai2 is the fraction of a day. The returned utc1 and utc2 form an analogous pair, except that a special convention is used, to deal with the problem of leap seconds - see the next note.

  2. JD cannot unambiguously represent UTC during a leap second unless special measures are taken. The convention in the present function is that the JD day represents UTC days whether the length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era there were smaller jumps (in either direction) each time the linear UTC(TAI) expression was changed, and these "mini-leaps" are also included in the ERFA convention.

  3. The function eraD2dtf can be used to transform the UTC quasi-JD into calendar date and clock time, including UTC leap second handling.

  4. The warning status "dubious year" flags UTCs that predate the introduction of the time scale or that are too far in the future to be trusted. See eraDat for further details.

Called:

   eraUtctai    UTC to TAI

References:

McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), IERS Technical Note No. 32, BKG (2004)

Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992)

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.