source: trunk/MagicSoft/slalib/dtt.c

#include "slalib.h"
#include "slamac.h"
double slaDtt ( double utc )
/*
**  - - - - - - -
**   s l a D t t
**  - - - - - - -
**
**  Increment to be applied to Coordinated Universal Time UTC to give
**  Terrestrial Time TT (formerly Ephemeris Time ET).
**
**  (double precision)
**
**  Given:
**     utc    double    UTC date as a modified JD (JD-2400000.5)
**
**  Result:  TT-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  Pre 1972 January 1 a fixed value of 10 + ET-TAI is returned.
**
**  3  See also the routine slaDt, which roughly estimates ET-UT for
**     historical epochs.
**
**  Called:  slaDat
**
**  Last revision:   6 December 1994
**
**  Copyright P.T.Wallace.  All rights reserved.
*/
{
   return 32.184 + slaDat ( utc );
}