gauss easter Algorithm
Latin: Carolus Fridericus gauss; 30 April 1777 – 23 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes referred to as the Princeps mathematicorum (Latin for'" the foremost of mathematicians"') and" the greatest mathematician since antiquity", gauss had an exceptional influence in many fields of mathematics and science, and is ranked among history's most influential mathematicians.
"""
https://en.wikipedia.org/wiki/Computus#Gauss'_Easter_algorithm
"""
import math
from datetime import datetime, timedelta
def gauss_easter(year: int) -> datetime:
"""
Calculation Gregorian easter date for given year
>>> gauss_easter(2007)
datetime.datetime(2007, 4, 8, 0, 0)
>>> gauss_easter(2008)
datetime.datetime(2008, 3, 23, 0, 0)
>>> gauss_easter(2020)
datetime.datetime(2020, 4, 12, 0, 0)
>>> gauss_easter(2021)
datetime.datetime(2021, 4, 4, 0, 0)
"""
metonic_cycle = year % 19
julian_leap_year = year % 4
non_leap_year = year % 7
leap_day_inhibits = math.floor(year / 100)
lunar_orbit_correction = math.floor((13 + 8 * leap_day_inhibits) / 25)
leap_day_reinstall_number = leap_day_inhibits / 4
secular_moon_shift = (
15 - lunar_orbit_correction + leap_day_inhibits - leap_day_reinstall_number
) % 30
century_starting_point = (4 + leap_day_inhibits - leap_day_reinstall_number) % 7
# days to be added to March 21
days_to_add = (19 * metonic_cycle + secular_moon_shift) % 30
# PHM -> Paschal Full Moon
days_from_phm_to_sunday = (
2 * julian_leap_year
+ 4 * non_leap_year
+ 6 * days_to_add
+ century_starting_point
) % 7
if days_to_add == 29 and days_from_phm_to_sunday == 6:
return datetime(year, 4, 19)
elif days_to_add == 28 and days_from_phm_to_sunday == 6:
return datetime(year, 4, 18)
else:
return datetime(year, 3, 22) + timedelta(
days=int(days_to_add + days_from_phm_to_sunday)
)
if __name__ == "__main__":
for year in (1994, 2000, 2010, 2021, 2023):
tense = "will be" if year > datetime.now().year else "was"
print(f"Easter in {year} {tense} {gauss_easter(year)}")
