def _next_fall_equinox(jd):
'''Return the julian day count of the previous fall equinox.'''
y, _, _ = gregorian.from_jd(jd)
eqx = Sun.get_equinox_solstice(y, "autumn").jde()
if eqx < jd:
eqx = Sun.get_equinox_solstice(y + 1, "autumn").jde()
return eqx
def gregorian_day_of_nawruz(year):
if year == 2059:
return 20
# get time of spring equinox
equinox = Sun.get_equinox_solstice(year, "spring")
# get sunset times in Tehran
latitude = Angle(35.6944)
longitude = Angle(51.4215)
# get time of sunset in Tehran
days = [19, 20, 21]
sunsets = list(
map(lambda x: Epoch(year, 3, x).rise_set(latitude, longitude)[1],
days))
# compare
if equinox < sunsets[1]:
if equinox < sunsets[0]:
return 19
else:
return 20
else:
if equinox < sunsets[2]:
return 21
else:
return 22
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_get_equinox_solstice():
"""Tests the get_equinox_solstice() method of Sun class"""
epoch = Sun.get_equinox_solstice(1962, target="summer")
y, m, d, h, mi, s = epoch.get_full_date()
st = "{}/{}/{} {}:{}:{}".format(y, m, d, h, mi, round(s, 0))
assert st == "1962/6/21 21:24:42.0", \
"ERROR: 1st get_equinox_solstice() test, time stamp doesn't match"
def gregorian_nawruz(year):
'''
Return Nawruz in the Gregorian calendar.
Returns a tuple (month, day), where month is always 3
'''
if year == 2059:
return 3, 20
# Timestamp of spring equinox.
equinox = Sun.get_equinox_solstice(year, "spring")
# Get times of sunsets in Tehran near vernal equinox.
x, y = Angle(TEHRAN[0]), Angle(TEHRAN[1])
days = trunc(equinox.get_date()[2]), ceil(equinox.get_date()[2])
for day in days:
sunset = Epoch(year, 3, day).rise_set(y, x)[1]
if sunset > equinox:
return 3, day
