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AstroUtilsJulianDateTT Method

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

Namespace:  ASCOM.Astrometry.AstroUtils
Assembly:  ASCOM.Astrometry (in ASCOM.Astrometry.dll) Version: 3c9121baba46811fe6e53a58a05935662261416d
public double JulianDateTT(
	double DeltaUT1


Type: SystemDouble
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

Type: Double
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

See Also