How is the Orthodox date for Easter determined?

Answer 1

The Easter or Pascha date is determined by four main factors. The first two have been established by Apostolic canon, making them binding, and the last two have been established by church tradition. The history of determining Easter dates has been complex and sometimes controversial, but the following pre-conditions provide a general summary. The Easter date is set according to the Julian or Old Calendar and this date must be: 1) after the Vernal (Spring) Equinox, and 2) after the Jewish Passover, and 3) with the first full moon in Spring, and 4) on a Sunday after 21 March.

Answer 2

You've probably noticed that we often have a different Easter/Pascha from all other Christians. Before our current calender was used, there was the older Roman calendar that relied on the lunar cycle. This calendar is also still used by the Jews. The Orthodox use this due to the fact that Jesus rode in on Pentecost and Pentecost was figured by the old lunar calendar. Therefore, we use the old calendar to calculate when Easter is as opposed to our current calendar which sometimes leads to us having Easter before Pentecost.