Easter: Does Anybody Really Know What Time It Is?
An odd thing happened this Easter: both western churches and Eastern Orthodox churches celebrated Easter on the same Sunday. This does not happen frequently, but why does eastern Easter often fall different than western? It dates (no pun intended) back to the Council of Nicea in 325 a.d., the same council that rendered the Nicene Creed. At that point the church and the world used the Julian Calendar and Easter was standardized as the first Sunday after the Passover. Previously, Easter, in some places has been celebrated on whatever day followed the Passover. The Jewish Passover is calculated based off lunar cycles; so it has come to be thought that Easter falls on the Sunday after the full moon after the vernal equinox. However, that’s not quite the case.
See, in 325 church astronomers calculated the dates of vernal full moons for the next 3000 years and established what is called the Paschal Full Moon. So, Easter is the first Sunday after the Paschal Full Moon, but the calculations were a bit off and so the Paschal Full Moon does not always coincide with a real full moon. Confused yet? Anyway, this was all fine and dandy until 1582 when Pope Gregory switched the world (at least the western part) to the Gregorian calendar. The Eastern Church stuck with the calculating the date of Easter based off of the Julian calendar. That’s why Eastern Orthodox Easter is often not on the same Sunday as Easter in western churches.
– Fr. Jason Emerson