Easter redux
March 28, 2008
We’ve been reading a lot about why Easter fell so early this year, and I’ve understood little of it. The words quoted below popped up on the web recently, presumably to put the issue to rest once and for all. So, for you inquiring minds, consider:
Easter is the date of the first Sunday after the first full moon on or after March 21… [T]he cycle of Easter dates repeat themselves every 5,700,000 years. The cycle of epacts (which encode the date of the full moon) in the Julian calendar repeat every nineteen years. There are two corrections made to the epact, each of which depend[s] only on the century; one repeats (modulo 30, which is what matters) every 120 centuries, the other every 375 centuries, so the [p]air of them repeat every 300,000 years. The days of the week are on a 400-year cycle, which doesn’t matter because that’s a factor of 300,000. So the Easter cycle has length the least common multiple of 19 and 300,000, which is 5,700,000 [years].
That clears it all up, right? Except for the first sentence, which I presume is factual (on the web you never know), I don’t find the explanation terribly helpful. I hope someone out there will parse the words and give me a hand. In the meantime, we always have timeanddate.com to fall back on. That tells us that Easter falls on April 12 next year, perhaps out of the snow zone for some of us.
Dave, calendar-challenged.
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