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# ut1utc

erfa.ut1utc(ut11, ut12, dut1)

  Time scale transformation: Universal Time, UT1, to Coordinated Universal Time, UTC.

  Parameters:
    ut11 double array
    ut12 double array
    dut1 double array
  Returns:
    utc1 double array
    utc2 double array

  Notes

  Wraps ERFA function `eraUt1utc`. The ERFA documentation is:

      - - - - - - - - - -
       e r a U t 1 u t c
      - - - - - - - - - -

      Time scale transformation:  Universal Time, UT1, to Coordinated
      Universal Time, UTC.

      Given:
         ut11,ut12  double   UT1 as a 2-part Julian Date (Note 1)
         dut1       double   Delta UT1: UT1-UTC in seconds (Note 2)

      Returned:
         utc1,utc2  double   UTC as a 2-part quasi Julian Date (Notes 3,4)

      Returned (function value):
                    int      status: +1 = dubious year (Note 5)
                                      0 = OK
                                     -1 = unacceptable date

      Notes:

      1) ut11+ut12 is Julian Date, apportioned in any convenient way
         between the two arguments, for example where ut11 is the Julian
         Day Number and ut12 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 Note 3.

      2) Delta UT1 can be obtained from tabulations provided by the
         International Earth Rotation and Reference Systems Service.  The
         value changes abruptly by 1s at a leap second;  however, close to
         a leap second the algorithm used here is tolerant of the "wrong"
         choice of value being made.

      3) JD cannot unambiguously represent UTC during a leap second unless
         special measures are taken.  The convention in the present
         function is that the returned quasi-JD UTC1+UTC2 represents UTC
         days whether the length is 86399, 86400 or 86401 SI seconds.

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

      5) 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:
         eraJd2cal    JD to Gregorian calendar
         eraDat       delta(AT) = TAI-UTC
         eraCal2jd    Gregorian calendar to JD

      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:  2023 May 6

      Copyright (C) 2013-2023, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.