Friday, April 22, 2011

A Late Easter This Year?

Lent and Easter are exceptionally late this year.
Now, you may ask: compared to what?
Well, the answer is compared to the range of dates that can accommodate Easter under the Easter dating method devised by Pope Gregory XIII and his astronomers and mathematicians.
According to the Gregorian calendar Easter is always one of the 35 dates between March 22 and April 25. The canonical rule is that Easter Day is the first Sunday after the 14th day of the lunar month (the nominal full moon) that falls on or after March 21 (nominally the day of the vernal equinox). So, this year Easter is almost as late as it can be. In 2009, Easter was exceptionally early and pretty much coincided with the first day of spring. Last year, it fell on April 12 -- just about where you might expect it.
One would also expect that this would be a warmer Easter this year -- certainly warmer than 2009.
But I actually remember balmy Easters in March and chilly Easters in April. And there have even been years when it has snowed on Easter Sunday, regardless of the date.
Why is the date of Christmas fixed while the date of Easter changes each year?
That's a question for another time.

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