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Easter: The floating holiday

By Keith McCord | Posted - Apr. 24, 2011 at 10:30 p.m.

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SALT LAKE CITY -- If it seems as though Easter came a little late this year, that's because it did.

Easter Sunday is a tough holiday to track -- it wanders all over the calendar. So what's the deal?

To find out, we asked our local astronomy buff and NASA ambassador -- Patrick Wiggins -- for an explanation.

"It's the first Sunday following the first full moon following the March Equinox," he said.

Sounds simple enough, but that formula also allows for significant calendar shifts of Easter. The day can vary by almost a month and a half depending on the year.

"It can happen as early as the 22nd of March or as late as the 25th of April," Wiggins said. "We're kind of butting up against the maximum late time."

Wiggins says there are two other schools of thought that come into play: the scientific and the ecclesiastical, which can alter the dates of the equinox as well as the occurrence of the full moon.

So, who came up with all this?

You have to go a long way back -- the rules determining the date for Easter were established by Roman Emperor Constantine in the year 325. The calendar was later revised by Pope Gregory XIII in 1582.

For those wanting a more detailed explanation, the U.S. Naval Observatory website has extensive information.

"That will bring up all the nitty gritty," said Wiggins. "But as I've been known to tell people, if you really want to know, look at the calendar."

For the math whizzes out there, there's a specific formula or algorithm that determines the day Easter will fall each year. The formula was created in 1940 and still works today.

For those wanting to plan ahead, Easter falls on April 8 next year and on March 31 in 2013.


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Keith McCord


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