In order to understand the dating conflict of Easter, we have to look at the issue of the calendar. Actually, the dating of Easter is complex and a result of using both lunar and solar calendars. The early Romans used a lunar calendar in which months alternated between 29 and 30 days. It was not a precise measure; it gradually fell out of step with the seasons. Julius Caesar reformed the calendar by switching its base from lunar to solar. The day on which the Vernal Equinox occurred was defined as March 25th. On the new Julian calendar, the length of the year was fixed at 365 days, with an additional leap-year day added every fourth year. This made the average length of a year equal to 365.25 days, which was fairly close to the actual value of 365.2422 days. The annual error of 0.0078 days accumulated over time until it became unmanageable. A second reform of the calendar was ordered by Pope Gregory XIII. Under the new system of the Gregorian calendar, March 21, 1582 CE became the date of the Vernal Equinox, and the year 1582 was shortened by ten days. This replacement did not occur until later in many countries; for example, on September 1752 in England. Of course, the Gregorian calendar continues in general usage today in the Western world.
The new Christians of the Western Church waited for Easter Sunday until the first Sunday on or after the next full moon. So today, among the Roman Catholic Church and Protestant denominations, Easter Sunday falls on the first Sunday after the first full moon after March 20, the nominal date of the Vernal or Spring Equinox. Thus, Easter Sunday can fall on any date from March 22 to April 25th. (However, it should be pointed out that Eastern Orthodox churches, using the Julian calendar, follow a different calculation. With Eastern Christianity’s Julian calendar, Easter always falls from April 4 to May 8 inclusive, which in the Gregorian calendar used by Western Christianity, due to the 13-day discrepancy of the calendars between 1900 and 2099, makes Easter Sunday fall anywhere from March 22 to April 25 inclusively. Eastern Orthodox churches sometime celebrate Easter on the same day as the Roman Catholics and Protestants. However if that date does not follow Passover, then the Orthodox churches delay their Easter—sometimes by over a month.) In Western Christianity, Easter marks the end of the forty days of Lent, a period of fasting and penitence in preparation for Easter, which begins on Ash Wednesday. The following day, Easter Monday, is a legal holiday in many countries, like Canada, with predominantly Christian traditions.
Again, the fact is that the precise dating of Easter has historically been a matter of contention for the Church. From early on. In June 325 CE, astronomers approximated astronomical full moon dates for the Christian church, calling them Ecclesiastical Full Moon (EFM) dates. From 326 CE the Paschal Full Moon (PFM) date has always been the EFM date after March 20, which was the Vernal Equinox date in 325 CE. Funny that this happened at 325 CE, since, coincidently enough, that was the exact date as The First Council of Nicaea, when a council of Christian bishops convened in Nicaea in (present-day Turkey) under the direction of the Roman Emperor Constantine I. At the First Council of Nicaea in 325 CE, it was decided that all Christians would celebrate Easter on the same day, which would be a Sunday. This first ecumenical council was an effort to attain consensus in the church through an assembly representing all of Christendom, applying to all Christendom. Of the four main accomplishments of this church council, the settling the calculation of the date of Easter was made official.
It is probable that no method of determining the exact date of Easter was specified by the Council of Nicaea. It did not, however, declare the Alexandrian or Roman calculations as normative. Instead, the Council gave the Bishop of Alexandria the privilege of announcing annually the date of Christian Passover to the Roman curia. Although the synod undertook the regulation of the dating of Christian Passover, it contented itself with communicating its decision to the different dioceses, instead of establishing a canon. Its exact words were not preserved, but from scattered notices we can make out that the Council ruled (1) that Easter must be celebrated by all throughout the world on the same Sunday; (2) that this Sunday must follow the fourteenth day of the moon; (3) that the moon was to be accounted the paschal moon whose fourteenth day followed the Vernal Equinox; (4) that some provision should be made, probably by the Church of Alexandria as best skilled in astronomical calculations, for determining the proper date of Easter and communicating it to the rest of the world. However, they made few decisions that were of practical use as guidelines for the computation, and it was several decades before the Alexandrine computations stabilized into their final form, and several centuries beyond that before a common method became accepted as normative throughout Christendom. The process of working out the details generated still further controversies. This became known as the “Easter Controversy.”
The problem was that it took a while for the Alexandrian rules to be adopted throughout Christian Europe. The Church of Rome continued to use an 84-year lunisolar calendar cycle from the late third century until 457 CE. The Church of Rome continued to use its own methods until the 6th century, when it may have adopted the Alexandrian method as converted into the Julian calendar. Early Christians in Britain and Ireland also used a late third century Roman 84-year cycle until the Synod of Whitby in 664 CE, when they adopted the Alexandrian method. Churches in western continental Europe used a late Roman method until the late 8th century during the reign of Charlemagne, when they finally adopted the Alexandrian method. However, with the adoption of the Gregorian calendar by the Catholic Church in 1582 and the continuing use of the Julian calendar by Eastern Orthodox Churches, the date on which Easter is celebrated again deviated, and continues to this day.
The official rule since the Middle Ages has been phrased as “Easter is observed on the Sunday after the first full moon on or after the day of the Vernal Equinox.” However, this does not reflect the actual ecclesiastical rules precisely. One reason for this is that the full moon involved (called the “Paschal Full Moon”) is not an astronomical full moon, but an ecclesiastical moon. Another difference is that the seasonal Vernal Equinox is a natural astronomical phenomenon, while the ecclesiastical Vernal Equinox is a fixed March 21. Therefore, the upshot of all this is that Easter is determined from tables that determine Easter based on the ecclesiastical rules described above, which approximate the astronomical full moon. But this, too, has not solved the calendrical discrepancy. In applying the ecclesiastical rules, the various Christian Churches use 21 March as their starting point from which they find the next full moon, etc. However, to repeat, because Eastern Orthodox and Oriental Orthodox Churches use the Julian calendar as their starting point, while Western Christianity uses the Gregorian Calendar the end point, the date for Easter usually diverges. But even within Western Christianity there is divergence. For instance, the Irish kept Easter on a different date from that of the Roman church (probably the original date of the festival of the goddess Ēostre), until the Roman calendar was imposed on them in 632 CE. (What is called the Alexandrine computus was finally adopted by the Irish colonies in northern Britain in the early 8th century due to the Christian monk and chronicler, the Venerable Bede of Northumbria, who fixed Easter to the Sunday falling in the seven-day period from the 14th to the 20th of its lunar month.) Nevertheless, the Columban foundation (a missionary Catholic society of apostolic life, founded in Ireland in 1916) and their colonies in Britain kept the old date for another fifty years.
I shall at this point attempt to go into greater detail about the dating of Easter with what is known as the “Easter Controversy.” The Easter Controversy is a series of controversies about the proper date to celebrate the Christian holiday of Easter. The history of this process of settling on a common date for Easter is long and compacted, but I will try to briefly give an accurate account of it. To date, there are four distinct historical phases of the dispute, which surprisingly enough, has yet to be resolved.
The first phase, which arose in the early 2nd century CE, was mainly concerned with whether Christians should follow Old Testament practices. Up until that time, the customary practice was to fix the celebration of Passover for Christians on the 14th day of the month of Nisan in the Old Testament’s Hebrew Calendar. (Nisan is the first month of the ecclesiastical year and the seventh month of the civil year on the Hebrew calendar. It is a spring month of 30 days, which usually falls in March–April on the Gregorian calendar.) This was the original method of fixing the date of the Passover, which was held to be a “perpetual ordinance.” According to the Gospel of John (John 19:14), this was the day that Jesus was crucified in Jerusalem. (However a slight discrepancy should be noted here, since the Synoptic Gospels place the day on the 15th day of Nisan.) The Latin Biblical term for this practice is Quartodecimanism. By the end of the 3rd century, however, some Christians had become dissatisfied with what they perceived as the disorderly state of the Jewish calendar. The chief complaint was that the Jewish practice sometimes set the 14th of Nisan before the Vernal Equinox.
That this ecclesiastical controversy was an early one in the Church is evidenced by a letter of St. Irenaeus, which shows that the diversity of practice regarding Easter had existed at least from the time of Pope Sixtus I (c. 120 CE). Further, Irenaeus states that the bishop of Smyrna, observed the fourteenth day of the moon, whatever day of the week that might be, following therein the tradition which he claimed to have derived from St. John the Apostle. Yet, for all this, around 195 CE, Pope Victor I attempted to excommunicate the Quartodecimans, turning the divergence of practice into a full-blown ecclesiastical controversy.
The second stage in the Easter controversy centers around the First Council of Nicaea in 325 CE. Given that the great Easter festival was always to be held on a Sunday and was not to coincide with a particular age of the moon (which might occur on any day of the week), a new dispute arose as to the determination of the Sunday itself, since Sundays can occur on any date of the month. Shortly before the Nicaean Council, in 314 CE, 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 Jewish custom. 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 Vernal 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 Vernal Equinox.
In an attempt to settle this confusion of discrepant Easter dates, 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, they made few decisions that were of practical use as guidelines for the computation, and it was several decades before the Alexandrine computations stabilized into their final form, and several centuries beyond that before a common method became accepted as normative throughout Christendom. The process of working out the details generated still further controversies.
The third stage in the Easter controversy centers around the Synod of Whitby. The Roman missionaries coming to Britain in the time of St. Gregory the Great (590–604 CE) found the British Christians and the Irish missionaries, who evangelized the English from the north, adhering to a system of Easter computation which differed from that used in the Mediterranean world. This British and Irish system, on the evidence of the 8th-century Christian monk and chronicler, the Venerable Bede of Northumbria, 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 method used by the Roman Church was Nisan 15 – Nisan 21. Any of these features alone could have led to occasional discrepancies from the date of Easter as computed by the Alexandrine method. This 84-year cycle (called the latercus) gave way to the Alexandrine computus in stages. The Alexandrine 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 Alexandrine computus over the Brittano-Irish cycle was decided at the Synod of Whitby in AD 664. The Alexandrine computus was finally adopted by the Irish colonies in northern Britain in the early 8th century, due to the work of the Venerable Bede. But what is important to note here is that the method from Alexandria became authoritative.
In its developed form it was based on the epacts (the ages of the moon) of a reckoned moon according to the 19-year cycle (a.k.a. the Metonic Cycle). The Alexandrian computus was converted from the Alexandrian calendar into the Julian calendar in Rome by Dionysius the Humble, though only for 95 years. Dionysius introduced the Christian Era (counting years from the Incarnation of Christ) when he published new Easter tables in 525 CE. Dionysius’s tables replaced earlier methods, based on 8 year and then 84 year cycles, used by the Church of Rome, as early as 222 CE. These old tables were used in Northumbria, the Venerable Bede’s birthplace, until 664 CE, and by isolated monasteries as late as 931 CE. A modified 84-year cycle was adopted in Rome during the first half of the 4th century. Victorius of Aquitaine tried to adapt the Alexandrian method to Roman rules in 457 CE in the form of a 532-year table, but he introduced serious errors. These Victorian tables were used in Gaul (now France) and Spain until they were displaced by Dionysian tables at the end of the 8th century.
In the British Isles Dionysius’s and Victorius’s tables conflicted with older Roman tables based on an 84-year cycle. The Irish Synod of Mag Léne in 631 CE decided in favor of either the Dionysian or Victorian Easter and the northern English Synod of Whitby in 664 CE adopted the Dionysian tables. The Dionysian reckoning was fully described by the Venerable Bede in his book, On the Reckoning of Time, an Anglo-Saxon era treatise written in Latin in 725 CE. He asserted that Easter was named after the Anglo-Saxon pagan goddess Ēostre or Eastra, who was worshiped during pre-Christian times as the Great Mother Goddess of the Saxon people in Northern Europe. Ēostre had a festival lasting several days, and this name was adopted in England for the Christian holiday of Easter. Thus we can also credit the dating of Easter to the Venerable Bede, who, as we have seen, was deeply interested in the long-standing Easter dating controversy. Through the account he gives of the controversy between the British and Anglo-Saxon churches over the correct method of obtaining the Easter date, he tried to scientifically calculate the date of Easter. (In brief, it should be explained here that Christianity reached Roman Britain by the third century of the Christian era, which meant that there came to be a distinction between the Roman and British churches. The British church, which included the Irish, developed traditions not found in the wider Christian world. Among these include a distinctive system for determining the dating of Easter distinct from the older Roman church. But soon a dispute arose with the British church between the native Britons and the Anglo-Saxons over the method of dating Easter. The Anglo-Saxons were the population in Britain partly descended from the Germanic tribes who migrated from continental Europe and settled the south and east of the island beginning in the early 5th century.) Bede, an Anglo-Saxon with some animus against the native Britons, wrote his famous historical chronicle, The Ecclesiastical History of the English People (731 CE), partly to show the unity of the English people and partly to disprove the British method of calculating Easter. Much of the work is devoted to a history of the dispute, including the final resolution at the Synod of Whitby in 664 CE. Yet this wasn’t the first work in which Bede took up the issue of the dating of Easter. Bede’s first treatise on historical and astronomical chronology was written in about 703 CE and entitled On Time. It provides an introduction to the principles of what he called Easter “computus” (Latin for “computation”). The next major work after this, in 725 CE, The Reckoning of Time (already cited), was influential throughout the Middle Ages. It includes a description of a variety of ancient calendars, including the Anglo-Saxon calendar, giving some information about its months. The focus of the work was the calculation of the date of Easter, which gave instructions for computing the date of Easter and the related time of the Easter Full Moon, and for calculating the motion of the Sun and Moon through the zodiac. The Dionysian/Bedan computus remained in use in Western Europe until the Gregorian calendar reform, and remains in use in most Eastern Churches, including most Eastern Orthodox Churches and Oriental Orthodox Churches. Churches beyond the eastern frontier of the former Byzantine Empire use an Easter that differs four times every 532 years from this Easter, including the Assyrian Church of the East.
After the promulgation of the Gregorian calendar in 1582 CE, the Catholic and Protestant churches of the West came to follow a different method of computing the date of Easter from the one that had been previously accepted. The Gregorian Easter has been used since 1583 by the Roman Catholic Church and was adopted by most Protestant churches between 1753 and 1845. German Protestant states used an astronomical Easter based on the Rudolphine Tables of Johannes Kepler between 1700 and 1774, while Sweden used it from 1739 to 1844. This astronomical Easter was one week before the Gregorian Easter in 1724, 1744, 1778, 1798, etc. Most Eastern Orthodox churches continued to follow the older practice and this difference has continued to the present time, despite several attempts 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. This reform has not yet been implemented, and thus the second century “Easter Controversy” lingers on.