The controversy over the correct date for Easter began in Early Christianity as early as the 2nd century AD. Discussion and disagreement over the best method of computing the date of Easter Sunday has been ongoing ever since and remain unresolved. Different Christian denominations continue to celebrate Easter on different dates, with Eastern and Western Christian churches being a notable example.
Main article: Quartodecimanism
Some see this first phase as mainly concerned with whether Christians should follow Old Testament practice; see also Christian views on the Old Covenant and Judaizers. Eusebius of Caesarea (Church History, V, xxiii) wrote:
A question of no small importance arose at that time [the time of Pope Victor I c. 190]. The dioceses of all Asia, according to an ancient tradition, held that the fourteenth day [τεσσαρεσκαιδεκάτην], on which day the Jews were commanded to sacrifice the lamb, should always be observed as the feast of the life-giving pasch (ἐπὶ ταῖς τοῦ σωτηρίου Πάσχα ἑορταῖς), contending that the fast ought to end on that day, whatever day of the week it might happen to be. However it was not the custom of the churches in the rest of the world to end it at this point, as they observed the practice, which from Apostolic tradition has prevailed to the present time, of terminating the fast on no other day than on that of the Resurrection of our Saviour.
Quartodeciman is an inflected Latin translation of [τεσσαρεσκαιδεκάτην] as in Eusebius's account above, meaning "Fourteenther", a person who practices fixing the celebration of Passover for Christians on the fourteenth (Latin quarta decima) day of Nisan, the first month of the Hebrew calendar (for example Lev 23:5). This was the original method of fixing the date of the Passover, which is to be a "perpetual ordinance". According to the Gospel of John (for example John 19:14), this was the day that Jesus was crucified in Jerusalem. (The Synoptic Gospels place the day on 15 Nisan, see also Chronology of Jesus.)
Irenaeus records the diversity of practice regarding Easter that had existed at least from the time of Pope Sixtus I (c. 120). He recorded Polycarp, the bishop of Smyrna, taught as the Asiatic churches did, thus by extension Polycarp must have observed the fourteenth day, following a tradition which he claimed to have derived from John the Apostle.
"Polycarp also was not only instructed by apostles, and conversed with many who had seen Christ, but was also, by apostles in Asia, appointed bishop of the Church in Smyrna, whom I also saw in my early youth, for he tarried [on earth] a very long time, and, when a very old man, gloriously and most nobly suffering martyrdom,(1) departed this life, having always taught the things which he had learned from the apostles, and which the Church has handed down, and which alone are true. To these things all the Asiatic Churches testify, as do also those men who have succeeded Polycarp down to the present time."
Around 195, Pope Victor I attempted to excommunicate the Quartodecimans, turning the divergence of practice into a full-blown ecclesiastical controversy. According to Eusebius, synods were convened and letters were exchanged, but in the end, having overstepped his mark, Victor, the Bishop of Rome, was rebuked and had to back down.
Polycrates of Ephesus (Greek: Πολυκράτης) was a bishop at Ephesus in the 2nd century who wrote a letter addressed to the Pope Victor I, Bishop of Rome, defending the Quartodeciman position in the Easter controversy.
Eusebius of Caesarea (Church History, V, xxiv) notes:
But this did not please all the bishops. And they besought him to consider the things of peace, and of neighborly unity and love. Words of theirs are extant, sharply rebuking Victor. Among them was Irenaeus, who, sending letters in the name of the brethren in Gaul over whom he presided, maintained that the mystery of the resurrection of the Lord should be observed only on the Lord’s day. He fittingly admonishes Victor that he should not cut off whole churches of God which observed the tradition of an ancient custom.
In 325 an ecumenical council, the First Council of Nicaea, established two rules: independence from the Jewish calendar, and worldwide uniformity. However, it did not provide any explicit rules to determine that date, writing only “all our brethren in the East who formerly followed the custom of the Jews are henceforth to celebrate the said most sacred feast of Easter at the same time with the Romans and yourselves [the Church of Alexandria] and all those who have observed Easter from the beginning.” Shortly before the Nicean Council, in 314, the Provincial Council of Arles in Gaul had maintained that the Lord's Pasch should be observed on the same day throughout the world and that each year the Bishop of Rome should send out letters setting the date of Easter.
The Syriac Christians always held their Easter festival on the Sunday after the Jews kept their Pesach. On the other hand, at Alexandria, and seemingly throughout the rest of the Roman Empire, the Christians calculated the time of Easter for themselves, paying no attention to the Jews. In this way the date of Easter as kept at Alexandria and Antioch did not always agree. The Jewish communities in some places, possibly including Antioch, used methods of fixing their month of Nisan that sometimes put the 14th day of Nisan before the spring equinox. The Alexandrians, on the other hand, accepted it as a first principle that the Sunday to be kept as Easter Day must necessarily occur after the equinox.
The Council of Nicaea ruled that all churches should follow a single rule for Easter, which should be computed independently of the Jewish calendar, as at Alexandria. However, it did not make any explicit ruling about the details of the computation, and it was several decades before the Alexandrine computations stabilized into their final form, and several centuries beyond that before they became normative throughout Christendom.
See also: Synod of Whitby
The Roman missionaries coming to Britain in the time of Pope Gregory I (590–604) found the British Christians adhering to a different system of Easter computation from that used in the Mediterranean basin. This system, on the evidence of Bede, fixed Easter to the Sunday falling in the seven-day period from the 14th to the 20th of its lunar month, according to an 84-year cycle. The limits of Nisan 14 – Nisan 20 are corroborated by Columbanus. The method used by the Roman Church was Nisan 15 – Nisan 21. The 84-year cycle, the lunar limits, and an equinox of March 25 also receive support from McCarthy's analysis of Padua, Biblioteca Antoniana, MS I.27. Any of these features alone could have led to occasional discrepancies from the date of Easter as computed by the Alexandrian method.
This 84-year cycle (called the latercus) gave way to the Alexandrian computus in stages. The Alexandrian computus may have been adopted in parts of the south of Ireland in the first half of the 7th century. Among the northern English, the use of the Alexandrian computus over the Brittano-Irish cycle was decided at the Synod of Whitby in 664. The Alexandrian computus was finally adopted by the Irish colonies in northern Britain in the early 8th century.
Main article: Reform of the date of Easter
After the Gregorian reform of the calendar by promulgation in 1582, the Roman Catholic Church continued to follow the same method for computing the date of Easter but the resulting date differed from that computed using the Julian Calendar due to the difference in time regarding when the vernal equinox was deemed to occur and when the relevant full moon fell. The Protestant churches of the Christian West all eventually adopted the Gregorian Calendar at various later stages. The Eastern Orthodox Church and the majority of the Christian East continue the older practice aligned to the Julian calendar.
Several attempts have sought to achieve a common method for computing the date of Easter.
In 1997 the World Council of Churches proposed a reform of the method of determining the date of Easter at a summit in Aleppo, Syria: Easter would be defined as the first Sunday following the first astronomical full moon following the astronomical vernal equinox, as determined from the meridian of Jerusalem. The reform would have been implemented starting in 2001, since in that year the Eastern and Western dates of Easter would coincide. But this reform was never implemented.