Easter is exactly when it should be…

Every year, I hear someone complaining about how Easter is too late, or Easter is too early. And the number of people that complain about how Easter can’t seem to have a fixed date… Every year, I respond to these complaints in the same fashion: You do know how Easter is calculated, don’t you? The blank stares are borderline hilarious.

Easter is always the first Sunday after the first full moon after the Spring Equinox. (Okay, the Spring Equinox for the Northern Hemisphere.) It’s a simple calculation really, or at least one would assume so, until they discover the truth behind the equation. While the description appears to be one based on astronomical events, it’s really not.

An equinox is the time of year when we have the same number of daylight hours that we do nighttime hours. However, the astronomical equinox can vary from the recognized date by up to two days every year. Notice I said recognized date. The equinox is nominally considered to be March 20th, however, for countries such as New Zealand, this date is actually the date before the astronomical equinox. For American Samoa, it’s the date after.

So, Easter is some time after March 20th, depending on when the first full moon is after this date. Yet, this is another descriptor that appears to be astronomically related, but actually isn’t.

Easter is based on the Paschal full moon, which is the fourteenth day of the ecclesiastical lunar month. (Isn’t that a mouthful to get your tongue around.) A lunar month can be between 29 and 30 days, intended to approximate the observed phases of the moon. However, a true lunar month, based on astronomical data, varies between 29.27 and 29.83 days. (How confusing can we get?)

So for the calculation of Easter, March 20th is the nominated date for the Spring Equinox and the first full moon after this is some calendar date that is based on a bizarre calculation that approximates the lunar phases (but can get it wrong by up to two full days).

But Easter is always a Sunday.

Let’s say that March 20th falls on a Friday, and the Paschal moon falls on March 21st. That means Easter can be as early as March 22nd. However, say the full moon before the equinox fell on March 20th itself. We then need to wait a full 29 days for the next full moon in the calculated sequence. As such Easter can be as late as April 25th.

It can really do the head in at times.

This year, 2016, the first full moon after the equinox is on March 24th. The first Sunday after that is on March 27th. So you see, Easter is not early; it’s exactly when it should be — even though the way they came to this date is incredibly confusing.


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Posted in Holidays, Science, Syrese Smalt and tagged , , .

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