The Greenwich Mean Time (GST) is the Greenwich hour angle of the mean equinox of date.
Calendar, Coordinated Universal Time, Ephemeris Time, Universal Time
Duffett-Smith, P. "Conversion of UT to GST," "Conversion of GST to UT," and "Converting LST to GST." §12-13 and 15 in Practical Astronomy with Your Calculator, 3rd ed. Cambridge, England: Cambridge University Press, pp. 17-19 and 21, 1992.
