One of the most frequent questions asked by and to Orthodox Christians is “Why does the Orthodox Church celebrate Easter on a different day than other Christians?” This difference has a long history related to Christianity itself, the complex nature of calendars, and the use of astronomical data.
Almost from the very beginning of the existence of the Christian Church, the issue regarding the date of our Lord’s death and resurrection presented variations. Although the New Testament relates these events to the Jewish Passover, the details of this relationship are not clear. On the one hand, the tradition of the Gospels of Matthew, Mark, and Luke identifies the Lord’s Last Supper with His disciples as a Passover meal.
This would place the death of our Lord on the day after Passover. On the other hand, the tradition of the Gospel of John situates the death of our Lord at the very hour the paschal lambs were sacrificed on the day of Passover itself. This variation in the interpretation of the Scriptures led to two different practices. The one observed Pascha on the day of Passover, regardless of the day of the week, that is a fixed date.
The other observed it on the Sunday following Passover. By the fourth century, the latter practice prevailed throughout the Church universally; nevertheless, differences continued to exist.
In response to this ongoing problem, the First Ecumenical Council, convened at Nicaea in 325 A.D., took up the issue. It determined that Pascha should be celebrated on the Sunday that follows the first full moon after the vernal equinox – the actual beginning of spring. If the full moon happens to fall on a Sunday, Pascha is observed the following Sunday. The day taken to be the invariable date of the vernal equinox is March 21.
Hence, the determination of the date of Pascha is governed by a process dependent on the vernal equinox and the phase of the moon. Another factor that figures prominently in determining the date of Pascha is the date of the Jewish Passover. Originally, Passover was celebrated on the first full moon after the vernal equinox.
Christians, therefore, celebrated Pascha according to the same calculation – that is, on the first Sunday after the first full moon following the vernal equinox. The correlation between the date of Pascha and the date of Passover is clear. Our Lord’s death and resurrection coincided with Passover, thereby assuring a secure point of reference in time. This assurance lasted, however, only for a short time.
Events in Jewish history contributing to the dispersion of the Jews had, as a consequence, a departure from the way Passover was reckoned at the time of our Lord’s death and resurrection. This caused the Passover to precede the vernal equinox in some years. It was, in fact, this anomaly that led to the condemnation reflected in Canon 1 of Antioch (ca. 330 A.D.) and Canon 7 of the Holy Apostles (late 4th century) of those who celebrate Pascha “with the Jews.”
The purpose of this condemnation was to prevent Christians from taking into account the calculation of Passover in determining the date of Pascha. Most Christians eventually ceased to regulate the observance of Pascha by the Jewish Passover.
Their purpose, of course, was to preserve the original practice of celebrating Pascha following the vernal equinox. Thus, the Council of Nicaea sought to link the principles for determining the date of Pascha to the norms for calculating Passover during our Lord’s lifetime.
Despite the intervention of the Council of Nicaea, certain differences in the technicalities of regulating the date of Pascha remained even thereafter. This resulted occasionally in local variations until, by the sixth century, a more secure mode of calculation based on astronomical data was universally accepted.
This was an alternative to calculating Pascha by the Passover and consisted in the creation of so-called “paschal cycles.” Each paschal cycle corresponded to a certain number of years. Depending upon the number of years in the cycle, the full moon occurred on the same day of the year as at the beginning of the cycle with some exceptions. The more accurate the cycle, the less frequent were the exceptions.
In the East, a nineteen-year cycle was eventually adopted, whereas in the West
an eighty-four-year cycle. The use of two different paschal cycles inevitably gave way to differences between the Eastern and Western Churches regarding the observance of Pascha.
A further cause for these differences was the adoption by the Western Church of the Gregorian Calendar in 1582 to replace the Julian Calendar. This took place in order to adjust the discrepancy, then observed between the paschal cycle approach to calculating Pascha and the available astronomical data.
The Orthodox Church continues to base its calculations for the date of Pascha on the Julian Calendar, which was in use at the time of the First Ecumenical Council. As such, it does not take into account the thirteen-day difference between the Julian and Gregorian Calendars.
Practically speaking, this means that Pascha may not be celebrated before April 3, which was March 21, the date of the vernal equinox, at the time of the First Ecumenical Council. In other words, a difference of thirteen days exists between the accepted date for the vernal equinox then and now.
Consequently, it is the combination of these variables that accounts for the different dates of Pascha observed by the Orthodox Church and other Christian Churches. If anything, this review of the complexities surrounding the issue of the date of Pascha underscores the compelling need to revisit it with patience and openness.
This topic has long been a concern of ecumenical dialogue. This was the spirit that predominated at a consultation on the matter held in Aleppo, Syria in 1997. One of its conclusions was that the underlying reason for the differences in the date of Pascha was the differences in the calendars and lunar tables (paschal cycles) employed rather than any theological disagreement between Eastern and Western Christians.
In view of the fact that today both the Julian and Gregorian modes of calculation diverge from the astronomical data, it behooves all Christians to return to the norms determined by the Council of Nicaea, taking advantage of the most up-todate astronomical data for the vernal equinox and the phase of the moon.