Easter Sunday, the greatest liturgical feast of the year, has been celebrated on various days throughout the Church's 2,000 year history. and the scheduling has provided more than its share of controversy.
From the very beginning of the Church the feast of the Resurrection of Our Lord was celebrated in relation with the Jewish feast of Passover. Since the events of Christ’s Passion and resurrection occurred in that context, Christians have always felt that they should celebrate his resurrection in the same way, rather than a fixed date on the calendar.
However, over the centuries Christians have disagreed over the calculation of Passover and the Christian celebration of Christ’s resurrection. This means Easter (though most often celebrated on a Sunday) is celebrated on different dates each year by various Christians.
Pope Francis, as well as other Christian leaders, has called for a unification of a celebration of Easter and has expressed his openness to changing the date of celebration for the sake of unity.
In essence there are two main arguments as to when Easter should be celebrated.
Western Christianity
According to the norms established by the Council of Nicaea (325) and later adopted for Western Christianity at the Synod of Whitby, Easter Sunday falls each year on the first Sunday following the first full moon after the vernal equinox.
This calculation accepted by the Roman Catholic Church and most Protestant communities does not depend on the calculation of Passover according to the Jewish calendar. There are several different rules that regulate the Jewish celebration of Passover. and Western Christians decided to differentiate themselves and rely on their own calculations.
Orthodox Calculation
As explained by Fr. Jon Magoulias at the Greek Reporter, the primary reason why the Orthodox calculation of Easter differs from the rest of Christianity is because the “Orthodox Church continues to follow the Julian calendar when calculating the date of Pascha (Easter). The rest of Christianity uses the Gregorian calendar. There is a 13-day difference between the two calendars, the Julian calendar being thirteen (13) days behind the Gregorian.”
Additionally, Fr. Magoulias notes that the Orthodox Church abides by a previous requirement that “Pascha must take place after the Jewish Passover in order to maintain the biblical sequence of Christ’s Passion. The rest of Christianity ignores this requirement, which means that on occasion Western Easter takes place either before or during the Jewish Passover.”
On occasion the two dates coincide, “when the full moon following the equinox comes so late that it counts as the first full moon after 21 March in the Julian calendar as well as the Gregorian...[which occurred] in 2010, 2011, 2014 and 2017."
This year, 2025, that coincidence also occurs, with all Christians, East and West, celebrating Easter on Sunday, April 20.
After meeting with Ecumenical Patriarch Bartholomew I in 2014, Pope Francis said to reporters, “Another thing we mentioned, that may be considered in the pan-Orthodox Council, is the date of Easter, because it is somewhat ridiculous to say, ‘When is your Christ resurrected? Mine was resurrected last week.’ Yes, the date of Easter is a sign of unity.”
Since then Pope Francis has expressed in other meetings with Orthodox Churches his desire for a unified celebration of Easter so that Christians could witness to the world more strongly.