Modified Oudin's Algorithm for Calculating the Date of Easter in the Gregorian Calendar

First published 1996 April 4; Last updated 2001 July 31 by M.J. Montes.
This is taken directly from an early version of the Calendar FAQ by Claus Tondering. The copyright and disclaimer from the document are:
Copyright and disclaimer
------------------------
        This document is Copyright (C) 1996 by Claus Tondering.
        E-mail: ct@login.dknet.dk.
        The document may be freely distributed, provided this
        copyright notice is included and no money is charged for
        the document.
 
        This document is provided "as is". No warranties are made as
        to its correctness.

The % operator
--------------
        Throughout this document the operator % will be used to
        signify the modulo or remainder operator. For example, 17%7=3
        because the result of the division 17/7 is 2 with a remainder
        of 3.

2.9.6. Isn't there a simpler way to calculate Easter? -----------------------------------------------------
Try this one (the divisions are integer divisions, in which remainders
are discarded):
 
century = year/100
G = year % 19
K = (century - 17)/25
I = (century - century/4 - (century - K)/3 + 19*G + 15) % 30
I = I - (I/28)*(1 - (I/28)*(29/(I + 1))*((21 - G)/11))
J = (year + year/4 + I + 2 - century + century/4) % 7
L = I - J
EasterMonth = 3 + (L + 40)/44
EasterDay = L + 28 - 31*(EasterMonth/4)
 
This algorithm is based on the algorithm of Oudin (1940) and quoted in
"Explanatory Supplement to the Astronomical Almanac", P. Kenneth
Seidelmann, editor.
Butcher's Algorithm for the calculation of the date of Easter.
Carter's Algorithm for the calculation of the date of Easter.
Gauss' Algorithm for the calculation of the date of the Orthodox Easter.
Calculation of the Ecclesiastical Calendar
Last updated 2001 July 31.
Marcos J. Montes
mmontes@no.spam.smart.net