mirror of
https://github.com/moparisthebest/SickRage
synced 2024-12-14 20:12:19 -05:00
92 lines
2.5 KiB
Python
92 lines
2.5 KiB
Python
"""
|
|
Copyright (c) 2003-2007 Gustavo Niemeyer <gustavo@niemeyer.net>
|
|
|
|
This module offers extensions to the standard Python
|
|
datetime module.
|
|
"""
|
|
__license__ = "Simplified BSD"
|
|
|
|
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))
|
|
|