Easter is one of the Christian religious holidays without a fixed worldly calendar date. It is celebrated on the first Sunday after the ecclesiastical full moon that occurs on or soonest after March 21. Easter season begins on Easter Sunday and lasts seven weeks. In 500 years (from 1600 to 2099 AD) Easter was and will be most often celebrated on either March 31 or on April 16 (22 times each). This year, the date falls on April 4.