Easter - Date

Date

Easter and the holidays that are related to it are moveable feasts, in that they do not fall on a fixed date in the Gregorian or Julian calendars (both of which follow the cycle of the sun and the seasons). Instead, the date for Easter is determined on a lunisolar calendar similar to the Hebrew calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the northern hemisphere's vernal equinox. Ecclesiastically, the equinox is reckoned to be on 21 March (even though the equinox occurs, astronomically speaking, on 20 March in most years), and the "Full Moon" is not necessarily the astronomically correct date.

In Western Christianity, using the Gregorian calendar, Easter always falls on a Sunday between 22 March and 25 April, inclusively. The following day, Easter Monday, is a legal holiday in many countries with predominantly Christian traditions.

Eastern Christianity bases its calculations on the Julian Calendar. Due to the 13-day difference between the calendars between 1900 and 2099, 21 March corresponds, during the 21st century, to 3 April in the Gregorian Calendar. Easter therefore varies between 4 April and 8 May on the Gregorian calendar (the Julian calendar is no longer used as the civil calendar of the countries where Eastern Christian traditions predominate). Among the Oriental Orthodox some churches have changed from the Julian to the Gregorian calendar and the date for Easter as for other fixed and moveable feasts is the same as in the Western church.

The precise date of Easter has at times been a matter for contention. At the First Council of Nicaea in 325 it was decided that all Christian churches would celebrate Easter on the same day, which would be computed independently of any Jewish calculations to determine the date of Passover. It is however probable (though no contemporary account of the Council's decisions has survived) that no method of determining the date was specified by the Council. Epiphanius of Salamis wrote in the mid-4th century:

...the emperor...convened a council of 318 bishops...in the city of Nicea...They passed certain ecclesiastical canons at the council besides, and at the same time decreed in regard to the Passover that there must be one unanimous concord on the celebration of God's holy and supremely excellent day. For it was variously observed by people....

In the years following the council, the computational system that was worked out by the church of Alexandria came to be normative. It took a while for the Alexandrian rules to be adopted throughout Christian Europe, however. The Church of Rome continued to use an 84-year lunisolar calendar cycle from the late 3rd century until 457. It then switched to an adaptation by Victorius of Aquitaine of the Alexandrian rules. Because this Victorian cycle differed from the Alexandrian cycle in the dates of some of the Paschal Full Moons, and because it tried to respect the Roman custom of fixing Easter to the Sunday in the week of the 16th to the 22nd of the lunar month (rather than the 15th to the 21st as at Alexandria), by providing alternative "Latin" and "Greek" dates in some years, occasional disagreements from the date of Easter as fixed by Alexandrian rules continued. The Alexandrian rules were adopted in their entirety in the 6th century. From this time, therefore, all disputes between Alexandria and Rome as to the correct date for Easter cease, as both churches were using identical tables.

Early Christians in Britain and Ireland also used an 84-year cycle. From the 5th century onward this cycle set its equinox to 25 March and fixed Easter to the Sunday falling in the 14th to the 20th of the lunar month inclusive. This 84-year cycle was replaced by the Alexandrian method in the course of the 7th and 8th centuries. Churches in western continental Europe used a late Roman method until the late 8th century during the reign of Charlemagne, when they finally adopted the Alexandrian method. Since 1582, when the Catholic Church adopted the Gregorian calendar while the Eastern Orthodox and most Oriental Orthodox Churches retained the Julian calendar, the date on which Easter is celebrated has again differed.