%N deltime %F $MIR/src/subs/ephem.for
%D Difference between UTC and some other time systems.
%P rjs
%: utilities
%B
        double precision function deltime(jday,sys)

        double precision jday
        character sys*(*)

  Determine the difference between UTC and some other time system.
  Leapseconds are also incoorporated in here. 
  For example

       double precision TAI,UTC
       TAI = UTC + deltime(UTC,'tai')

  Input:
    jday       UTC time when the difference is required.
    sys        The time system. Possible values are:
               'tai'   International atomic time.
               'tdt'   Terrestial dynamical time. )
               'tdb'   Barycentric dynamical time.) Taken as identical.
               'et'    Ephemeris time.            )
               'tt'    Terrestial time            )
               'utc'   Coordinated universal time.
  Output:
    deltime    The time difference, T - UTC, in days.
