Pope Leo XIV and the Search for a Common Easter

Pope Leo XIV has spent the early months of his papacy pursuing a specific project: narrowing the theological fractures that have divided Catholic and Orthodox Christianity since the Great Schism of 1054. In November 2025, he and Ecumenical Patriarch Bartholomew I signed a joint declaration in Istanbul committing both churches to dialogue toward full communion. Among the specific commitments in that declaration was finding a common date for Easter, a problem the two churches have failed to resolve for more than four centuries. It is part of a broader project to heal long-standing divisions between the two largest branches of Christianity.

Easter and the Passover question

Easter is the most important holiday in the Christian calendar, marking the resurrection of Jesus Christ. According to the Synoptic Gospels, Jesus was arrested and crucified during Passover, the Jewish festival of liberation observed on the 14th of Nisan in the Jewish lunar calendar. The earliest Christian communities organized their celebration of the resurrection in relation to that date. By the late second century, two competing practices had emerged and were dividing the church.

Churches in Asia Minor, drawing on a tradition they attributed to the Apostle John, celebrated Easter on the 14th of Nisan itself, regardless of what day of the week it fell on. These communities were called Quartodecimans, from the Latin for “fourteenth.” Rome celebrated on the Sunday following the 14th of Nisan, arguing that Sunday carried theological weight as the day of the resurrection and that Easter should always fall on it.

Around 190 AD, Pope Victor I threatened to excommunicate the Asian churches for refusing to conform to Roman practice. Eusebius of Caesarea, writing in his Ecclesiastical History, records that the controversy was “no small dispute.”¹ At the center of it was the question that would define the Easter date debate for the next seventeen centuries: who has the authority to determine how the resurrection of Christ is observed?

The Council of Nicaea

Constantine convened the First Council of Nicaea in 325 AD primarily to address the Arian controversy, the theological dispute over whether Christ was fully divine. Easter was explicitly on the agenda. His letter summarizing the council’s Easter decision states the motivation plainly: “It appeared an unworthy thing that in the celebration of this most holy feast we should follow the practice of the Jews, who have defiled their hands with a most atrocious crime.”² The formula the council established was designed to make Easter independent of the Jewish calendar: the first Sunday after the first full moon following the vernal equinox. Every Christian community accepted it, and for more than twelve centuries it held.

The 1582 break

The formula agreed at Nicaea did not change in 1582. What changed was the calendar used to calculate it. The Julian calendar, introduced by Julius Caesar in 46 BC, sets the solar year at 365.25 days. The actual solar year is 11 minutes and 14 seconds shorter. Over 1,257 years, that discrepancy accumulated into a drift of roughly ten days, meaning the vernal equinox was falling in early March rather than March 21. Pope Gregory XIII commissioned a correction. The Gregorian calendar dropped ten days from October 1582 and adjusted the leap year rule.

Catholic countries adopted the reform. The Orthodox churches rejected it, and the rejection was not about the astronomy. It was about jurisdiction: a unilateral papal decree does not bind churches that do not recognize papal authority. The Julian calendar continues to govern Easter calculations across Eastern Christianity. Because it now runs thirteen days behind the Gregorian, the two churches calculate their first full moon after the vernal equinox from different starting points. In most years, those produce different Easters. The Nicaea formula is unchanged. The division it produced is institutional, not doctrinal.

The 1997 attempt

The most structured modern effort to close the gap came at a 1997 consultation in Aleppo, Syria, jointly sponsored by the World Council of Churches and the Middle East Council of Churches. The proposal replaced the calendar question with an astronomical one: Easter would be the first Sunday after the first astronomical full moon following the astronomical vernal equinox, calculated from the meridian of Jerusalem. This preserved the Nicaea formula while making it calendar-agnostic. For Western Christians, the date would change in only a handful of years. For Eastern Christians, it would change in approximately 70 percent of years.⁵

The proposal asked the Orthodox to change their practice in roughly 70 percent of years while the Catholic Church changed in almost none. It did not fail because the formula was wrong. It failed because it reproduced the structure of the original dispute: a process that required one church to move on terms the other had effectively set.

Why now

Leo moved on the Easter date in June 2025, at a symposium marking the 1,700th anniversary of the Council of Nicaea. He described two churches marking the resurrection on different days as causing “pastoral problems within communities, dividing families, and weakening the credibility of our witness to the Gospel.”⁴ In November, the joint declaration he signed with Patriarch Bartholomew in Istanbul converted that statement into a formal shared commitment.³ Easter 2025 had fallen on the same date for both churches, April 20, one of the infrequent years in which the two calendars converge naturally. The next aligned dates are April 16, 2028, April 13, 2031, and April 9, 2034.

What it adds up to

Two billion Christians marked the resurrection of Christ on different days in 2024. The formula that should unify that date has been agreed since 325 AD. What has kept it split is not theology but a calendar reform imposed without consent in 1582, and four centuries of neither institution conceding to terms the other could accept. Leo and Bartholomew have now signed a joint commitment to find a different path. Whether the institutions follow is the remaining question, but it is the first time in thirty years that question has been worth asking.³