def equinox_jd(gyear):
"""Calculate Julian day during which the March equinox, reckoned from the
Tehran meridian, occurred for a given Gregorian year."""
mean_jd = Sun.get_equinox_solstice(gyear, target='spring')
deltat_jd = mean_jd - Epoch.tt2ut(gyear, 3) / (24 * 60 * 60.)
# Apparent JD in universal time
apparent_jd = deltat_jd + (Sun.equation_of_time(deltat_jd)[0] / (24 * 60.))
# Correct for meridian of Tehran + 52.5 degrees
return floor(apparent_jd.jde() + (52.5 / 360))
def test_sun_equation_of_time():
"""Tests the equation_of_time() method of Sun class"""
epoch = Epoch(1992, 10, 13.0)
m, s = Sun.equation_of_time(epoch)
assert abs(m) - 13 < TOL, \
"ERROR: 1st equation_of_time() test, 'm' doesn't match"
assert abs(round(s, 1)) - 42.6 < TOL, \
"ERROR: 2nd equation_of_time() test, 's' doesn't match"