Why is the Eastern Orthodox celebrated at a different time from the rest of the Christian World?
The main reason for the Orthodox Churches to keep the Julian Calendar for Easter, even when the fix-day celebrations are according to Gregorian Calendar, is that Resurection Day must always be after the Jewish Passover. With Western/Gregorian style computations, it comes not only on the same date, but often quite earlier, which is unacceptable for the Orthodox Church.
