greenwichMeanSiderealTime function

double greenwichMeanSiderealTime(
  1. double jdUt,
  2. double jdTT
)

Greenwich mean sidereal time (radians, 0 ≤ GMST < 2π): the Earth rotation angle θ for jdUt plus the angle from the CIO to the mean equinox of date at jdTT, from the long-term precession model (Vondrák, Capitaine and Wallace 2011; see longTermGmstMinusEra).

Implementation

double greenwichMeanSiderealTime(double jdUt, double jdTT) =>
    (earthRotationAngle(jdUt) +
        longTermGmstMinusEra(centuriesSinceJ2000(jdTT))) %
    (2 * math.pi);