How is the Easter Date Set?
by Dr. Lewis J. Patsavos

The determination of the date of Easter is governed by a process dependent on the Vernal Equinox and the phase of the moon. According to the ruling of the First Ecumenical Council in 325, Easter Sunday should fall on that Sunday which follows the first full moon after the Vernal Equinox. If the full moon happens to fall on a Sunday, Easter is observed the following Sunday. The day taken to be the invariable date of the Vernal Equinox is March 21.

Herein lies the first difference in the determination of Easter between the Orthodox Church and the other Christian Churches. The Orthodox Church continues to base its calculations for the date of Easter on the Julian Calendar, which was in use at the time of the First Ecumenical Council. As such, it does not take into consideration the number of days which have since then accrued due to the progressive loss of time in the Julian Calendar. Practically speaking, this means that Easter may not be celebrated before April 3, which was March 21 - the date of the Vernal Equinox - at the First Ecumenical Council. In other words, a difference of 13 days exists between the accepted date for the Vernal Equinox then and now.

In the West, this discrepancy was addressed in the 16th century through the adoption of the Gregorian Calendar, which adjusted the Julian Calendar still in use by all Christians at that time. Western Christians, therefore, observe the date of the Vernal Equinox on March 21, according to the Gregorian Calendar. Some Orthodox Churches, among which is the Ecumenical Patriarchate under whose jurisdiction lies the Greek Orthodox Archdiocese of North and South America, adopted the Gregorian Calendar 60 years ago for all immovable feastdays (Christmas, Epiphany, Annunciation, etc.). For the feast of feasts - Easter - however, and the movable feasts dependent upon it (Palm Sunday, Ascension, Pentecost, etc.), most Orthodox Churches still abide by the Julian Calendar.

The other difference in the determination of Easter between the Orthodox and other Christian Churches concerns the date of Passover. Jews originally celebrated Passover the first full moon following the Vernal Equinox. Christians, therefore, celebrated Easter on the first Sunday after the first full moon following the Vernal Equinox. After the destruction of Jerusalem in 70 A.D. and other tragic events which gave rise to the dispersion of the Jews, Passover sometimes preceded the Vernal Equinox. This was occasioned by the dependence of the dispersed Jews upon local pagan calendars for the calculation of Passover. As a consequence, most Christians eventually ceased to regulate the observance of Easter by the Jewish Passover. Their purpose, of course, was to preserve the original practice of celebrating Easter following the Vernal Equinox.

As an alternative to calculating Easter by the Passover, "paschal (Easter) cycles" were devised. Depending upon the number of years of the cycle, the full moon occurs 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 are the exceptions. The Eastern Church eventually adopted a 19-year cycle, the Western Church an 84-year cycle. The use of two different "paschal cycles" inevitably gave way to differences between the Eastern and Western Churches regarding the observance of Easter. Varying dates for the Vernal Equinox increased these differences.

All this points to the urgent need to reexamine the method of calculating our Easter along the lines of modern astronomical data. A revision of both the date of the Vernal Equinox and the Paschal Cycle to determine the phases of the Moon must be taken seriously into consideration. These were the recommendations of the consultation convened in 1977 at the Patriarchal Center in Chambesy, Switzerland to examine the calendar question. There is much evidence to support the correctness of these recommendations.