Compute the date of Easter Sunday for both the Western (Gregorian) and Eastern (Orthodox/Julian) traditions using the Meeus/Jones/Butcher algorithm. Also shows related movable feasts (Ash Wednesday, Palm Sunday, Good Friday, Ascension, Pentecost), and can print a table across a range of years.
Easter is the first Sunday after the first ecclesiastical full moon on or after March 21. The Western church uses the Gregorian calendar and the Meeus/Jones/Butcher "anonymous" algorithm (valid for any Gregorian year). The Eastern Orthodox church still bases the full-moon date on the Julian calendar; this tool computes the Julian date and then converts it to the modern Gregorian date. Between 1583 and 2099, Orthodox Easter falls 4, 5, or 35 days after Western Easter, or on the same day roughly 30% of the time.