I came to this conversation a bit late, but I don't understand:
The reason the Western churches and the Orthodox churches celebrate Easter in different weeks is due to the Orthodox churches' still using the Julian calendar for their calculation. This year, they happen to fall in the same week -- rare event.
The date of Easter, calculated as given, shouldn't depend on the calendar. The equinox is an astronomical thing, it is when the days and nights have the same length, and whether I call it "March 21" and you call it "March 7" or not, it happens at the same time. The full moon following it also doesn't care what date it is. And though the calendars do not agree on dates, the days of the week are parallel in both calendars (aren't they?), so the first Sunday after the first full moon after the vernal Equinox is still the same Sunday, whether you name it "April 15" or "April 1" or some other thing altogether.
I don't recall the Ukrainian half of my family celelbrating Easter at a different time. Christmas, yes, but not Easter...at least I don't think so! Someone please explain this!
