Computation of GAST, GMST, and ERA

This service computes GAST (Greenwich Apparent Sidereal Time), GMST (Greenwich Mean Sidereal Time), and ERA (Earth Rotation Angle), time-related quantities required for, e.g., many uses of our APFS service. To learn more, see the service info or the web page of the IERS.

To compute the current values, leave the form empty. Otherwise, enter a date expression (for UT1; only a subset of the available operators is supported) and an interval (in seconds) for how often a date should be computed.


Date and time (UT1)
Interval between two sets of computed values