Easter and the holidays that are related to it are moveable feasts which do not fall on a fixed date in the Gregorian or Julian calendars which follow only the cycle of the sun; rather, its date is determined on a lunisolar calendar similar to the Hebrew calendar. The First Council of Nicaeaestablished two rules, independence of the Jewish calendar and worldwide uniformity, which were the only rules for Easter explicitly laid down by the council. No details for the computation were specified; these were worked out in practice, a process that took centuries and generated a number of controversies. It has come to be the first Sunday after the ecclesiastical full moon that occurs on or soonest after 21 March, but calculations vary in East and West. Details of this complicated computation are found below in the section Date.
Easter is linked to the Jewish Passover by much of its symbolism, as well as by its position in the calendar. In many languages, the words for “Easter” and “Passover” are identical or very similar. Easter customs vary across the Christian world, and include sunrise services, exclaiming the Paschal greeting, clipping the church, and decorating Easter eggs, a symbol of the empty tomb.The Easter lily, a symbol of the resurrection, traditionally decorates the chancel area of churches on this day and for the rest of Eastertide. Additional customs that have become associated with Easter and are observed by both Christians and some non-Christians include egg hunting, the Easter Bunny, and Easter parades. There are also various traditional Easter foods that vary regionally.