Easter date is a moving feast. It is defined as the first Sunday after the Full Moon after the Vernal Equinox. The epact (number of phase days of the Moon in the beginning of the year) is the basis of the computation. The epact is estimated differently by Eastern and Western Christian Church. Also the Style (Calendar) used is not the same: Julian for Orthodox and Gregorian for Catholics. These result usually to a different Easter date in Easter and Western Christians
Easter Computus
Select a year after 325 AD (Synod of Nicaea) to compute the date of the Orthodox/ Catholic Easter
