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

Namespace: ASCOM.Astrometry.SOFA
Assembly: ASCOM.Astrometry (in ASCOM.Astrometry.dll) Version: 6.0.0.0 (6.1.1.2619)

Syntax

C#
public int TaiUtc(
	double tai1,
	double tai2,
	ref double utc1,
	ref double utc2
)
Visual Basic
Public Function TaiUtc ( _
	tai1 As Double, _
	tai2 As Double, _
	ByRef utc1 As Double, _
	ByRef utc2 As Double _
) As Integer
Visual C++
public:
virtual int TaiUtc(
	double tai1, 
	double tai2, 
	double% utc1, 
	double% utc2
) sealed

Parameters

tai1
Type: System..::..Double
TAI as a 2-part Julian Date (Note 1)
tai2
Type: System..::..Double
TAI as a 2-part Julian Date (Note 1)
utc1
Type: System..::..Double%
UTC as a 2-part quasi Julian Date (Notes 1-3)
utc2
Type: System..::..Double%
UTC as a 2-part quasi Julian Date (Notes 1-3)

Return Value

Status: +1 = dubious year (Note 4), 0 = OK, -1 = unacceptable date

Remarks

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 SOFA convention.
  3. The function iauD2dtf 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 iauDat for further details.

See Also