Reform of the date of Easter refers to proposals to change the date for the annual celebration of Easter. These proposals include setting a fixed date or agreeing between Eastern and Western Christendom a common basis for calculating the date of Easter so that all Christians celebrate the Festival on the same day. As of 2022, no such agreement has been reached. Description A reform of the date of Easter has been proposed several times because the current system for determining the date of Easter is seen as presenting two significant problems: Its date varies from year to year. It can fall on up to 35 days in March and April of the respective calendar. While many Christians do not consider this to be a problem, it can cause frequent difficulties of co-ordination with civil calendars, for example academic terms. Many countries have public holidays around Easter weekend or tied to the date of Easter but spread from February to June, such as Shrove Tuesday or Ascension and Pentecost. Many Eastern churches calculate the date of Easter using the Julian calendar, whereas some Eastern churches use the Revised Julian calendar and all Western churches and civil authorities have adopted the Gregorian reforms for all calendrical purposes. Hence in most years, Easter is celebrated on a later date in the East than in the West. There have been controversies about the "correct" date of Easter since antiquity, but most Christian churches today agree on certain points. Easter should therefore be celebrated: on a Sunday according to the Council of Nicaea in 325, after the Northward equinox, which ecclesiastically is on 21 March in the Gregorian calendar; that is in Northern Hemisphere spring and Southern Hemisphere autumn, after the nominal "Paschal" full moon. There is less agreement whether Easter also should occur: so that Annunciation—celebrated 25 March, 9 months before Christmas—does not fall on any day from the Sunday before Easter to the Sunday after, on or after the 14th day of the lunar month of Nisan, not before Jewish Pesach – Easter is after Christian Passover by definition. The disagreements have been particularly about the determination of moon phases and the equinox, some still preferring astronomical observation from a certain location (usually Jerusalem, Alexandria, Rome or local), most others following nominal approximations of these in either the Hebrew, Julian or Gregorian calendar using different lookup tables and cycles in their algorithms.