Easter Weather & History

April 21, 2011

Easter Saturday should be spectacular, Sunday not so much, but here is the forecast:

Easter IS unusually late this year.  Jim Todd sent this great bit of Easter information to us today.  Jim runs the Planetarium at OMSI.  I’ve always had a keen interest in history…if you do as well, you might want to read on…

This question comes up every year, with a bit of puzzlement, too. But for this year in particular, many people have commented on Easter’s. Do you know why the holiday’s date changes each year? Other major holidays throughout the year have set days: July 4th; Labor Day; Christmas, etc.  It’s often hard to comprehend Easter’s association with the Vernal Equinox, the full moon, and Sunday.

Each year, Easter’s date bounces around the calendar.  Why is this?  In 325 A.D., The Council of Nicaea, commonly regarded as the first Ecumenical council of the Christian Church, convened in ancient Nicaea (now Iznik,Turkey) at the request of Constantine I. His goal for the council was to restore order in the young religion of Christianity, then beset with internal disagreements and controversy.  

As a side note, the council was also instructed to arrive at a means for calculating the annual observance of Easter, which at the time coincided with the Jewish holiday of Passover. Throughout Constantine I’s kingdom, the Christian Passover or Easter was observed on different dates. Attributed to Pope Saint Soter and followed by believers in Alexandria and Romewas the formula which is followed today: Easter is observed on the first Sunday after the first full moon following the vernal equinox. This neatly avoided following any particular calendar, and staggered both Jewish and Christian holidays.

 How did the moon get involved in all this?  The number of lunar cycles in a year is uneven.  This means that the time of the Passover celebration is a moveable feast during the month of March and April.  The council of Nicaea involved the full moon to provide the pilgrims, who traveled to Jerusalem, with a bright night sky in order to assure their safety.

 For Easter in 2011, the vernal equinox is on March 20, the time when the sun is directly over the equator.  The full moon for March is on the 19th, before the equinox.  In April, the full moon is on Sunday the 17th.  But church astronomers added further stipulation that if the first full moon occurred on a Sunday, then Easter should be celebrated the following Sunday.  In this case, Easter 2011 will be on Sunday, April 24.  This is just a day short of latest date possible of April 25.  The last time this occurred was in 1943 and the next time it falls on April 25 is the year 2038.  The earliest date is on March 22 which happened in 1818 and will not happen again until 2285.