Jimmy Westlake: A late Easter this year | SteamboatToday.com

Jimmy Westlake: A late Easter this year

The date of Easter Sunday can be as early as March 22 or as late as April 25, depending on when the first full moon of spring happens. This year, the full moon on April 15 makes our April 20 Easter Sunday one

Have you ever wondered why the date of Easter Sunday hops around from year to year? Sometimes it falls in March and sometimes, in April. In fact, Easter Sunday can come as early as March 22 or as late as April 25. In 2008, Easter Sunday fell on March 23, almost as early as it can be. Now, six years later, Easter Sunday falls on April 20, almost as late as it can be. What's going on here?

The oft-stated rule for determining the date of Easter Sunday is this: Easter is the first Sunday after the first full moon that falls on or after the March equinox, or the first day of spring in the Northern Hemisphere. This rule usually will predict the correct date for Easter, but sometimes it doesn't. The ancient (and correct) rule for determining the date of Easter Sunday also is tied to the date of the full moon, but not to the date of the March equinox.

Easter is the date on which Christians traditionally celebrate the resurrection of Jesus. Scholars think that Jesus was crucified sometime between the years 27 AD and 33 AD, during the time of the Jewish festival of Passover, which is celebrated during the time of the first full moon of spring.

In the year 325 AD, early Christians decided that they wanted all Christians in the world to celebrate Easter at the same time, preferably on a Sunday. They created a table of predicted full moon dates, called Paschal or Easter full moons, that stretched far into the future.

The actual dates of the full moons can differ from these calculated dates by several days, but they are usually close. At that time, Easter Sunday was declared to be the Sunday immediately following the Paschal full moon each year.

There have been a few modern attempts by various Christian denominations to pin down the date of Easter Sunday to always occur on the second Sunday in April, but all of these attempts have fallen flat.

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The Paschal full moon in 2014 falls on Monday, making the following Sunday as Easter Sunday.

The real full moon falls on Tuesday in Colorado, and it is the first full moon to follow the equinox on March 20, so both rules point to the same date for Easter Sunday in 2014, April 20.

The latest possible Easter, on April 25, last happened in 1943, and that won't happen again until the year 2038. Until then, according to the website http://www.timeanddate.com, there will be one more April 20 Easter in 2025, and an April 21 Easter in 2019 and 2030. Our Easter this year is one of the latest in the next two decades.

I hope that your late Easter is a happy one.

Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Westlake's astrophotography website at http://www.jwestlake.com.

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