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from datetime import date, timedelta

class LiturgicalYear:
def __init__(self, year, v2 = False):
#v2 = "Vatican II" and refers to the reforms made to the calendar
#which were adopted my many Protestant denominations in the 1970's
#The only significant change for our purposes, is the date of
#Transfiguration Sunday, which in turn is used to calculate the number
#of Sundays after Epiphany.
self.init_calendar(year, v2)

def calc_easter(self, year):
"Returns easter as a date object."
a = year % 19
b = year // 100
c = year % 100
d = (19 * a + b - b // 4 - ((b - (b + 8) // 25 + 1) // 3) + 15) % 30
e = (32 + 2 * (b % 4) + 2 * (c // 4) - d - (c % 4)) % 7
f = d + e - 7 * ((a + 11 * d + 22 * e) // 451) + 114
month = f // 31
day = f % 31 + 1
return date(year, month, day)

def init_calendar(self, year, v2 = False):
self.vatican2 = v2
self.easter = self.calc_easter(year + 1)

#The first Sunday in Advent is always on or after November 27th
nov27day = date(year, 11, 27).isoweekday()
if nov27day == 7:
else:
self.advent1 = date(year, 11, 27) + timedelta(7 - nov27day)

#Now calculate the date of the next First Sunday in Advent in order to
#calculate Sundays after Trinity.
nov27day = date(year + 1, 11, 27).isoweekday()
if nov27day == 7:
next_advent1 = date(year + 1, 11, 27)
else:
next_advent1 = date(year + 1, 11, 27) + timedelta(7 - nov27day)

#First Sunday after Epiphany
jan6day = date(year + 1, 1, 6).isoweekday()
if jan6day == 7:
self.epiphany1 = date(year + 1, 1, 13)
else:
self.epiphany1 = date(year + 1, 1, 13) - timedelta(jan6day)

#A bunch of easy ones:
self.epiphany = date(year + 1, 1, 6)
if v2:
self.transfiguration = self.easter - timedelta(49)
else:
self.transfiguration = self.easter - timedelta(70)
self.septuagesima = self.easter - timedelta(63)
self.ashWednesday = self.easter - timedelta(46)
self.maundyThursday = self.easter - timedelta(3)
self.goodFriday = self.easter - timedelta(2)
self.palmSunday = self.easter + timedelta(7)
self.ascension = self.easter + timedelta(39)
self.pentecost = self.easter + timedelta(49)
self.trinity = self.easter + timedelta(56)
self.pentecostLast = self.trinityLast

#Sundays after Epiphany and Trinity/Pentecost
#Note: Epiphany Sundays include Transfiguration
self.epiphanySundays = (self.transfiguration - self.epiphany1).days / 7 + 1
self.trinitySundays = (next_advent1 - self.trinity).days / 7 - 1
self.pentecostSundays = self.trinitySundays + 1

#And finally, American Thanksgiving - which shouldn't even be here,
#but too many people complain if it's not:
nov1day = date(year + 1, 11, 1).isoweekday()
if nov1day <= 4:
self.thanksgiving = date(year + 1, 11, 26 - nov1day)
else:
self.thanksgiving = date(year + 1, 11, 33 - nov1day)