Christians commemorated Easter — that is, Jesus’ resurrection — annually, from very early on in the faith’s history. Unfortunately, we do not have any explicit descriptions of such celebrations dating any earlier than the 2nd century. So the details of how it was observed, and when, are a bit unclear.
What we do know is that the specific dating of Easter varied among Christian communities.
Unlike doctrinal and dogmatic disagreements that could, on occasion, emerge inside a single Christian group or congregation, how Easter was dated tended to be decided regionally. That is, whole districts of Christians observed Easter on the same date, but how they dated it in one province may have been different from another province, further away.
In particular, Christians of Asia Minor and parts of Syria and the Levant dated Easter according to the traditional Jewish calendar, pegging it to the 14th day of the Jewish month of Nisan. This coincided with Jewish Passover, and they celebrated it no matter what day of the week it was. These Christians were called quartodecimani, from the Latin quartodecimus meaning “fourteen.”
Quartodecimans claimed apostolic pedigree for their tradition. Specifically, they claimed 14 Nisan had been set as the date of Easter by the apostles John or Philip.
In other regions, particularly in the western Empire and in the environs of Alexandria, other dates were used, but they always celebrated Easter on a Sunday. The churches of Rome, for example, famously celebrated Easter on the Sunday following the first full moon after the vernal equinox. Christians who celebrated Easter always on a Sunday often objected to the Quartodeciman dating because it smacked of Judaizing.
This variation was remarked upon but doesn’t appear to have been viewed, at least initially, as a serious conflict. Writing in the 4th century, Eusebius reports that Polycarp and Pope Anicetus discussed the matter, when the former visited Rome. They were unable to reach a consensus. Anicetus conceded that the eastern bishops could follow their own tradition but that the rest of Christendom should follow Rome’s.
Christians who celebrated Easter only on a Sunday didn’t always agree on which Sunday it should fall. There were inconsistencies among districts, which were based on varying specifications as well as the degree to which astronomical distinctions could be made. This became a significant issue, in some cases.
In Rome, at one point, Easter was said to fall on the first Sunday after the first full moon following the vernal equinox. Thus, planning for Easter meant knowing in advance the dating of full moons. This information wasn’t always available to everyone in the Greco-Roman world. Sure, it was possible to look up at the moon on any given night, note its phase, then perhaps guess how many days remained until it would be full again. But planning any more than a month ahead required better information than that.
The bottom line is that, even Christians who ostensibly agreed on how Easter should be dated, didn’t always observe it on the same date. This caused problems that festered over the years.
As with so many other aspects of Christianity, disagreements over Easter tended to worsen and grow more hostile over time. Polycarp and Anicetus agreeing to disagree was no longer enough, a few generations later. In particular, those who celebrated Easter always on a Sunday objected increasingly to the Quartodeciman practice, with its dependence on the Jewish calendar (largely for that reason).
Also, the number of variations of dating Easter became problematic. Even Christians who agreed on the same definition didn’t always come up with the same dates, partly because they worked from different astronomical tables. Something had to be done … and it was, in the early 4th century.
Among the issues discussed during the Council of Nicaea in 325 CE, was the dating of Easter. While we don’t have the exact text of the decision made, we do know some decisions were made, and a general framework was adopted, that the entire Church was to follow. It was rather open.
These were the only points agreed upon at Nicaea. Other specifics may have been discussed but they were not included in the final result (as far as we know). All of this, however, was enough to go on, for a while at least.
Shortly after Nicaea, it became a tradition — for a time — that the Patriarchs of Constantinople declared when Easter was to be celebrated, each year. This is due to presence of astronomical academies in that city, which were widely respected and depended upon for many matters (not just the dating of Easter) in the Greco-Roman world.
The Alexandrian patriarchs, starting with Athanasius in 329, issued annual letters announcing when Easter was to be celebrated. These were called “festal letters.” They were typically mundane, and while most were preserved, not all have survived. Still, on the occasion of writing to Christendom, the patriarchs sometimes had more to say than just when Easter was to be held, and some of them are of historical interest.
For instance, in his 39th festal letter (for the year 367), Athanasius laid out what he considered the sacred scriptures for the Church to revere and follow. He listed, rather famously, the 27 books of the now-common New Testament. He also listed works that were to be viewed as important and helpful, but were not quite at the same level, and still others that were unacceptable.
In the century or so following the framework pronounced at Nicaea, Christians in various locations came up with tables of future dates for Easter, based on lunar predictions available to them. Although Nicaea had declared that all Christians should observe Easter on the same date each year, in practice, this didn’t always happen.
These schedules weren’t unprecedented, though. During the early 3rd century, an 84-year cycle of dates was devised by Hippolytus of Rome. Other cycles were devised, including a 14-year cycle and a 532-year table of dates, as well.
All of these early tables proved faulty, at some point pegging Easter too early (particularly, prior to the vernal equinox) or too late (so that Pentecost, set as 50 days after Easter, fell on an unacceptable date). This is why Alexandrian patriarchs became the sources for Easter’s dating in the 4th century. They decided it annually, rather than trying to project the dates on a long-term schedule or cycle.
Over time, better ways of calculating Easter in advance were devised, and dependence on the Alexandrian patriarchs diminished, but as before, these systems tended to vary regionally. Churches in the British Isles celebrated it according to their own schedule, as did Christians of other areas. As the Middle Ages rolled on, though, especially with the Popes of Rome gaining ascendance over the western Church as a whole, these variants melted away.
But that doesn’t mean there are no more variations. As noted, despite the decision at Nicaea that all Christians should celebrate Easter on the same date each year, this doesn’t happen, even now, centuries later with our extensive — not to mention accurate — astronomical data.
In the wake of an explosion of astronimical science, during the 16th century, Pope Pregory XIII the Roman Catholic Church reformed the calendar entirely. That included its specifications for how Easter was dated. Western Christendom, including nearly all Protestant sects, follow Gregory’s calendar. Under this system, Easter can be as early as March 22 and as late as April 25.
The Orthodox churches of the east, however, retained their own calendars. Under that system, Easter is on a Sunday following the first full moon after Jewish Passover. Orthodox Easter can fall anywhere between April 4 and May 8. (By a very rare coincidence, in 2025, Easter fell on April 20 according to both of these schedules.)
You’ve probably noticed two things: First, that Nicaea’s directive that all Christians observe Easter on the same date isn’t being followed; and second, that decoupling Easter from the Jewish calendar also isn’t followed, at least explicitly within the Orthodox churches.
You would be entirely correct to notice this. As it turns out, Nicaea produced a nice idea, but one that Christians, over time, simply could not, or would not, live up to in practice.
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