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.

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