#!/usr/bin/env sage -python
#
# ComputeEaster: Compute date of Easter Sunday in the Gregorian calendar.
#
# Adapted from an example in _Introducing Fortran 95_ by Chivers and Sleighthome,
# which was itself adapted from an example by Donald Knuth.
#
# Stephen Forrest, http://wandership.ca/

def ComputeEaster(Year):
    Metcyc = (Year % 19) + 1
    if Year <= 1582:
        Day = (5*Year) // 4
        Epact = ((11*Metcyc-4) % 30) + 1
    else:
        Century = (Year // 100)+1
        Error1 = ((3*Century) // 4)-12
        Error2 = ((8*Century+5) // 25)-5
        Day = ((5*Year) // 4)-Error1-10
        Temp = 11*Metcyc + 20 + Error2 - Error1
        Epact = Temp % 30
        if Epact <= 0:
            Epact = 30 + Epact
        if ((Epact==25 and Metcyc>11) or Epact==24):
            Epact = Epact+1
        Luna = 44 - Epact
        if Luna < 21: Luna = Luna+30
        Luna = Luna+7 - ((Day+Luna) % 7)
        if Luna > 31:
            return( 'April %(date)d' % {'date': Luna-31} )
        else:
            return( 'March %(date)d' % {'date': Luna} )

# Examples
print ComputeEaster( 1938 )
print ComputeEaster( 2007 )