Volume 2 (2014)

First page of the paper.

Proceedings of the first egyptological conference of the Patriarchate of Alexandria

The Epact Computation: An Alexandrian Achievement for All Christian World

Hanna, Atif Naguib


One of the many significant original achievements of Abba Dēmētrios I (12th Patriarch of the See of Saint Mark in Alexandria: 189-231 AD) was the method he devised for calculating the Date of Easter so that it would always follow the Passover, just like the Rest Easter Sunday, according to the historical biblical events. This method is known as the Epact, and to this day it is followed by all Eastern Orthodox Churches in determining their Easter date very many years in advance. It involved making a correlation between the lunar (Semitic) year and the solar (Egyptian) year. This was necessary because the lunar year is shorter than the solar year by eleven days, and a fixed date in it can fall in any season as the years go by, and would deviate Easter from the Passover. When Abba Dēmētrios performed the Epact Computation, he convoked the Holy Synod, and explained it to its Members. They approved it and decided to abide by it. Many years later, in 325 AD, when the 1st Œcumenical Council of Nikaia met, this computation was submitted to it, and was again unanimously accepted. It continued to be followed by all Christian Churches until 1582 AD, when the calendar was changed by Pope Gregorius XIII of Rome. Since then the Western Churches departed from it, and now they observe Easter on the first Sunday after the Full Moon following the Vernal Equinox, regardless of the Passover. All the Eastern Churches, however, still adhere to this old computation (Computus), hence the divergence between the Eastern and Western Churches on the Date of Easter celebration persists.


Hanna, A.N. 2014. «The Epact Computation: An Alexandrian Achievement for All Christian World», JHIE 2: 223–231



Language: en


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