Python/other/gauss_easter.py
Maxim Smolskiy b5cb1fba0d
Enable ruff DTZ005 rule ()
* Enable ruff DTZ005 rule

* Fix other/gauss_easter.py

* Fix

* Fix web_programming/instagram_pic.py

* Fix web_programming/instagram_video.py

* Apply suggestions from code review

* Update instagram_pic.py

* datetime.now(tz=UTC).astimezone()

* .astimezone()

* Fix

---------

Co-authored-by: Christian Clauss <cclauss@me.com>
2024-03-25 21:54:11 +01:00

61 lines
1.9 KiB
Python

"""
https://en.wikipedia.org/wiki/Computus#Gauss'_Easter_algorithm
"""
import math
from datetime import UTC, 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, tzinfo=datetime.timezone.utc)
>>> gauss_easter(2008)
datetime.datetime(2008, 3, 23, 0, 0, tzinfo=datetime.timezone.utc)
>>> gauss_easter(2020)
datetime.datetime(2020, 4, 12, 0, 0, tzinfo=datetime.timezone.utc)
>>> gauss_easter(2021)
datetime.datetime(2021, 4, 4, 0, 0, tzinfo=datetime.timezone.utc)
"""
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, tzinfo=UTC)
elif days_to_add == 28 and days_from_phm_to_sunday == 6:
return datetime(year, 4, 18, tzinfo=UTC)
else:
return datetime(year, 3, 22, tzinfo=UTC) + timedelta(
days=int(days_to_add + days_from_phm_to_sunday)
)
if __name__ == "__main__":
for year in (1994, 2000, 2010, 2021, 2023, 2032, 2100):
tense = "will be" if year > datetime.now(tz=UTC).year else "was"
print(f"Easter in {year} {tense} {gauss_easter(year)}")