JulianDateTT Method
Current Julian date based on the terrestrial time (TT) time scale

Namespace: ASCOM.Astrometry.AstroUtils
Assembly: ASCOM.Astrometry (in ASCOM.Astrometry.dll) Version: (


public double JulianDateTT(
	double DeltaUT1
Visual Basic
Public Function JulianDateTT ( _
	DeltaUT1 As Double _
) As Double
Visual C++
virtual double JulianDateTT(
	double DeltaUT1
) sealed


Type: System..::..Double
Current value for Delta-UT1, the difference between UTC and UT1; always in the range -0.9 to +0.9 seconds. Use 0.0 to calculate TT through TAI. Delta-UT1 varies irregularly throughout the year.

Return Value

Double - Julian date on the UT1 timescale.


When Delta-UT1 is provided, Terrestrial time is calculated as TT = UTC + DeltaUT1 + DeltaT. Otherwise, when Delta-UT1 is 0.0, TT is calculated as TT = UTC + ΔAT + 32.184s, where ΔAT is the current number of leap seconds applied to UTC (34 at April 2012, with the 35th being added at the end of June 2012). The resulting TT value is then converted to a Julian date and returned.

Forecast values of Delta-UT1 are published by IERS Bulletin A at http://maia.usno.navy.mil/ser7/ser7.dat

See Also