On 25/3/03 8:16 am, Eugene van der Pijll at [EMAIL PROTECTED] spake thus: > 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. [*]
Tøndering 2.12.2 (Excerpt): (Note, however, that historically, some countries have used the real (astronomical) full moon instead of the official one when calculating Easter. This was the case, for example, of the German Protestant states, which used the astronomical full moon in the years 1700-1776. A similar practice was used Sweden in the years 1740-1844 and in Denmark in the 1700s.) I've decided (for now) to ignore these exceptions. In fact all historical information is being ignored. My module will currently tell you the date for Easter in 500BC! (April 14th) > First of all, they use a formula for the full moon based on the Golden > Number instead of the Astronomical full moon. Actually, the golden number is used in calculating any Easter - there's a number associated with each year. There's 19 golden numbers and its calculated as: $GoldenNumber = ($year % 19) + 1 It's the Epact that changes based on the Moon. The Epact is the age of the moon (the number of days that have passed since an 'official' new moon) at the start of the year. (In Jullian 8+Epact is the age at the start of the year) > 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. Once again, this 'theoretical' equinox is used in both calendars, however as the Julian calendar is slowly slipping away from the Gregorian (I hadn't realised that until this morning) the date for the Vernal Equinox is similarly slipping. > There's a formula for Orthodox Easter in Claus Tondering's FAQ, which is > linked from http://datetime.perl.org . I've looked through there a dozen times, in fact that's where the calculations in DateTime::Event::Easter came from! I just missed it for some reason. > 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. Yeah .. part of my missreading on the Orthodox Easter Thanks for all this. Really helps, although I can see I'll have to use DateTime::Calendar::Julian to calculate these dates. Which hurts: I'm an anti-dependency kind of guy :) Cheers! Rick -------------------------------------------------------- There are 10 kinds of people: those that understand binary, and those that don't. -------------------------------------------------------- The day Microsoft makes something that doesn't suck is the day they start selling vacuum cleaners --------------------------------------------------------
