The various liturgical calendars in use throughout most of Christianity feature a happy coincidence in 2025: Easter Sunday will be celebrated on the same day in almost every Christian church, be it Protestant, Catholic or Eastern Orthodox. Due to the alignment of the lunar cycles that determine the date of Christianity’s primary feast in both the Julian and Gregorian calendars, April 20 is this year an almost universal celebration for followers of Christ and believers in his good news. It will happen again in 2028, but in most years, the date of Easter varies widely between East and West, sometimes by as much as a month.
It wasn’t always this way. As Pope Francis noted during the Week of Prayer for Christian Unity in January of this year, Christians shared an established formula for calculating the date of Easter for more than 12 centuries until the Catholic Church adopted the Gregorian calendar in 1582. Like Pope Paul VI half a century ago, however, Pope Francis has indicated his willingness to accept a common date for the celebration of Easter with the Christian churches of the East going forward. (Almost all Protestant churches already celebrate Easter on the same day as Roman Catholics.)
Celebrating Easter together might seem like a simple expression of union, but it can also breathe new life into efforts toward true Christian unity and the fulfillment of Jesus’ prayer in John 17:21, “so that they may all be one, as you, Father, are in me and I in you, that they also may be in us, that the world may believe that you sent me.”
That such an initiative is underway just as the Christian churches celebrate the 1,700th anniversary of the Council of Nicaea is not by chance, for it was at that momentous ecumenical gathering that the early church fathers determined that Easter would be celebrated on the first Sunday after the first moon following the vernal equinox. Nicaea was also where the early Christians agreed upon a standard expression of their shared beliefs: the Nicene Creed. It remains unchanged still today; even the later variation in that creed in the Western churches—the filioque clause—is almost always omitted by Western Christians during shared celebrations with their Eastern brothers and sisters who do not include it.
To recognize this anniversary of the Council of Nicaea, Pope Francis made plans to travel to Turkey at the end of May, including a meeting with Bartholomew I, the Eastern Orthodox patriarch of Constantinople. Meetings between popes and patriarchs might appear so commonplace today as to seem not even newsworthy, but we should not forget that less than a century ago, such a meeting would have been unthinkable. When Ecumenical Patriarch Athenagoras of Constantinople met with Pope Paul VI in Jerusalem in 1964, it was the first time such a meeting had occurred in over five centuries. While tensions between the Eastern patriarchs—largely over the Russian invasion of Ukraine—could make this year’s meeting a fraught one, the symbolic value of the gathering is still powerful.
In a world marked by division and strife, the kind of consistency of accord that the Council of Nicaea brought about is no small thing. Every person of faith can surely admit that religion has often been a cause of conflict between different peoples or nations, and the history of Christianity is no exception to that sad reality. Christian wars of religion may be largely a thing of the past, but still today our ecumenical efforts—to say nothing of our interreligious ones—can be marred by rancor and distrust. The Council of Nicaea and its 17-century legacy are, in that sense, also beacons of hope for the future.
The first step toward greater union between Christians is to acknowledge that unity does not have to mean uniformity. The path toward unity does not lie down the road of claiming there are no differences between the Christian churches or that the differences do not matter. Nor is it reasonable to expect—or even want—every Christian to experience liturgy or prayer in the same way in every place. We cannot expect our Orthodox brothers and sisters to accept every structure and tradition that has developed in the Roman Catholic Church over the past millennium since the Great Schism of 1054; nor would most Catholics be willing to do the same with regard to either Orthodox or Protestant practices.
At the same time, Christians can acknowledge what we share, beginning with the Nicene Creed but including much more. For almost all the churches, our shared understandings include a common baptism; and for Catholics and the Orthodox, a mutual recognition of the validity of each others’ sacraments, including ordination and, most importantly, the Eucharist.
Our celebration of Nicaea and our recognition of what we share in common can also offer us another important lesson: Unity is not always born in harmony. The end result of Nicaea might have been the establishment of a common creed, but the council itself was hardly an occasion of peaceful or complete agreement. Rather, theological disputes about the nature of Jesus—particularly over the view known as Arianism—were threatening to tear the early church asunder, and the council was called in large part to settle those questions. It did so only after intense debate and occasional physical violence among the more than 300 bishops present.
In other words, Nicaea teaches us that efforts in the expectation of unity can be messy. As long as Christians differ in their theology, ecclesiology, structures of worship and more, we can hardly expect such differences to disappear with the signing of a document or an exchange of affection. But the end result of engaging in good faith with the difficult questions and convictions at stake can still be—as it ultimately was at Nicaea—a greater unity among us all.
As we journey through Lent in the expectation of our shared celebration of Easter this year, we join together in a prayer Pope Francis offered during an ecumenical prayer service in Rome in January. Calling the anniversary of the Council of Nicaea “a year of grace, an opportunity for all Christians who recite the same Creed and believe in the same God,” Francis prayed: “Let us rediscover the common roots of the faith; let us preserve unity! Let us always move forward! May the unity we all are searching for be found.”
