Rick Measham schreef: > They're always around the same time as the western Easter, the > Equinox doesn't change .. its still on Gregorian March 21st (or if > they observe the astronomical equinox they *might* observe March > 22nd), and they get the next Astronomical full moon after that which > only ever differs by a day or two. Thus Easter can only ever be a > week earlier or later IIRC.
I believe that is wrong on several counts. I've been reading up on the Eastern Orthodox calendar, and it's a mess; but the date of Easter is the one thing they agree on. [*] First of all, they use a formula for the full moon based on the Golden Number instead of the Astronomical full moon. Secondly, they use a theoretical equinox, which is fixed on the 21st of March, Julian. This means the possible dates for Easter will drift by 0.75 days per century. As the difference between their equinox and the astronomical one is now two weeks, they must wait for one more full moon in about 50% of the years. This means a difference of about four weeks between the western and eastern Easters. There's a formula for Orthodox Easter in Claus Tondering's FAQ, which is linked from http://datetime.perl.org . There have been attempts to introduce a new Easter formula in both branches of Christianity. This is based on the true astronomical equinox and the astronomical full moon, and is calculated in Jerusalem local time. But this is controversial, and won't be accepted in the near future. Eugene [*] Except the Orthodox Church of Finland, which uses the western Easter dates. Or so I've read somewhere.
