FM / dateutil

/usr/lib/python3.6/site-packages/dateutil/

/usr/lib/python3.6/site-packages/dateutil

Name	Size	Mode	Actions
tz/	-	0755	rm
zoneinfo/	-	0755	rm
__pycache__/	-	0755	rm
easter.py	2629	0644	edit dl rm
parser.py	50939	0644	edit dl rm
relativedelta.py	23145	0644	edit dl rm
rrule.py	61835	0644	edit dl rm
tzwin.py	59	0644	edit dl rm
_common.py	768	0644	edit dl rm
_version.py	219	0644	edit dl rm
__init__.py	69	0644	edit dl rm

Edit: /usr/lib/python3.6/site-packages/dateutil/easter.py (2629B)

# -*- coding: utf-8 -*-
"""
This module offers a generic easter computing method for any given year, using
Western, Orthodox or Julian algorithms.
"""

import datetime

__all__ = ["easter", "EASTER_JULIAN", "EASTER_ORTHODOX", "EASTER_WESTERN"]

EASTER_JULIAN = 1
EASTER_ORTHODOX = 2
EASTER_WESTERN = 3

def easter(year, method=EASTER_WESTERN):
    """
    This method was ported from the work done by GM Arts,
    on top of the algorithm by Claus Tondering, which was
    based in part on the algorithm of Ouding (1940), as
    quoted in "Explanatory Supplement to the Astronomical
    Almanac", P.  Kenneth Seidelmann, editor.

This algorithm implements three different easter
    calculation methods:

1 - Original calculation in Julian calendar, valid in
        dates after 326 AD
    2 - Original method, with date converted to Gregorian
        calendar, valid in years 1583 to 4099
    3 - Revised method, in Gregorian calendar, valid in
        years 1583 to 4099 as well

These methods are represented by the constants:

* ``EASTER_JULIAN   = 1``
    * ``EASTER_ORTHODOX = 2``
    * ``EASTER_WESTERN  = 3``

The default method is method 3.

More about the algorithm may be found at:

http://users.chariot.net.au/~gmarts/eastalg.htm

and

http://www.tondering.dk/claus/calendar.html

"""

if not (1 <= method <= 3):
        raise ValueError("invalid method")

# g - Golden year - 1
    # c - Century
    # h - (23 - Epact) mod 30
    # i - Number of days from March 21 to Paschal Full Moon
    # j - Weekday for PFM (0=Sunday, etc)
    # p - Number of days from March 21 to Sunday on or before PFM
    #     (-6 to 28 methods 1 & 3, to 56 for method 2)
    # e - Extra days to add for method 2 (converting Julian
    #     date to Gregorian date)

y = year
    g = y % 19
    e = 0
    if method < 3:
        # Old method
        i = (19*g + 15) % 30
        j = (y + y//4 + i) % 7
        if method == 2:
            # Extra dates to convert Julian to Gregorian date
            e = 10
            if y > 1600:
                e = e + y//100 - 16 - (y//100 - 16)//4
    else:
        # New method
        c = y//100
        h = (c - c//4 - (8*c + 13)//25 + 19*g + 15) % 30
        i = h - (h//28)*(1 - (h//28)*(29//(h + 1))*((21 - g)//11))
        j = (y + y//4 + i + 2 - c + c//4) % 7

# p can be from -6 to 56 corresponding to dates 22 March to 23 May
    # (later dates apply to method 2, although 23 May never actually occurs)
    p = i - j + e
    d = 1 + (p + 27 + (p + 6)//40) % 31
    m = 3 + (p + 26)//30
    return datetime.date(int(y), int(m), int(d))

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