Hi -- Being a Russian Orthodox priest, I can answer the Easter calculation. Not that that's a prerequisite. But in the Church, you hear all sorts of mistaken opinions about why the dates are different. Both the Western and Eastern churches have the same rule: first Sunday after first full moon after spring equinox. But all of the events are based on calculations, not on observations. One of three things happens: 1. The two are a month apart -- this happens because the equinox is figured as a fixed date. The Eastern Churches figure this date on the Julian calendar (even though most Orthodox Churches don't use the Julian for fixed holidays; Russian Church does), so it's April 3 instead of March 20. 2. Some years the difference in equinoxes doesn't matter, but the full moon calculations slightly differ. In these years, Orthodox Easter is one week later. So something like first full moon after March 20 is also after April 3, but it falls on Saturday, and the formulas used by the Orthodox perhaps mark it as falling on Sunday, so Orthodox Easter ends up a week later. 3. In some years, the first full moon after Gregorian Equinox falls after Julian Equinox, and falls early enough in the week not to throw anything off. That's what happened this year. The first full moon after March 20 was also after April 3, and it fell on a Monday. I believe there are some years in which, from a perfectly astronomical point of view, both dates are wrong. Theoretically, this would happen when the moon hits full at something like 23:59 on Saturday, but even the more recent Western calculations had it occurring at 0:01... To the best of my knowledge, no Christian church updates its Easter computations year-to-year based on the most up-to-date measurements. If I am correct, Jewish passover is based on the Julian equinox as well. ---- Rev. Michael A. van Opstall Department of Mathematics, University of Utah Office: JWB 313 opstall@math.utah.edu