15.5.300 gst06a

gst06a(jdut, jdtt)

[SOFA] Returns Greenwich apparent sidereal time in radians consistent with IAU 2000 and 2006 resolutions. jdut is the Julian Date (UT1). jdtt is the Julian Date (TT) of the same instant. jdut is needed to predict the Earth rotation, and TT to predict the effects of precession. If jdtt is set equal to jdut then errors of order 100 microarcseconds result. jdut and jdtt must have the same dimensions. The result has those same dimensions as well.

See also: Astronomical Coordinate Calculations