Why Does Eastern Orthodoxy (and Eastern Catholicism) Celebrate Easter on Different Days from Latin Rite Catholics?
Well, there are a couple answers. First of all, it's not always on a different Sunday! In 2010 and 2011, for example, Eastern and Western Christians celebrated Easter on the same weekend. This happens with relative frequency too (see chart below). But why the differences?
Well one difference is that the Eastern Rite Catholics and Orthodoxy use the Julian Calendar while Latin Rite Catholics (and Protestantism too) uses the Gregorian Calendar.
Some believe the reason for the difference is related to anti-semitism in Orthodoxy, especially in the early years. Actually, both East and West celebrated Easter on the same day from 325ad to 1582ad when the Latin Church fully adopted the Gregorian Calendar and Orthodoxy remained with the Julian Calendar. So while there was, no doubt, some anti-Jewish sentiments going around in the Early Church, neither side was immune to this.
Easter 2010 to 2020