When I was in elementary school, I asked my teacher why the date of Easter changed from year to year, unlike the date of Christmas, which is always on December 25th. She told me that the date of Easter depends upon which company prints the calendars.
Why the date of Easter changes is somewhat more complicated. Always on a Sunday, Easter cannot occur earlier than March 22 or later than April 25, and that is just in the Western churches (Catholic and Protestant churches, although some Protestant churches do not celebrate Easter).
The Eastern Orthodox churches follow the Julian Calendar (in contrast to the Gregorian calendar used in the Western church), which differs by thirteen days, so in the Gregorian calendar (the calendar that is used throughout the world, even being the official calendar in Eastern Orthodox countries), the date of Easter in the Eastern Orthodox churches occurs between April 4 and May 8.
It took centuries for the churches to agree on the date of Easter, finally settling on the definition that the date of Easter is the date of the first Sunday after the full moon after the vernal equinox, which is assumed to occur on March 21, although astronomically, the date of the equinox varies.
The moon is part of the calculation of the Biblical association of the date of Easter with the Jewish holiday Passover, which also varies on the Gregorian calendar, because the Jewish calendar is based on the movement of the moon, while the Gregorian and Julian calendars are based on the movement of the sun.
The precise date of Easter has at times been a matter for hearty disagreement among Christian churches. At the first ecumenical council of Nicaea in 325 (the council at which the “Nicene Creed” was first formulated), the bishops decided that all Christians would celebrate Easter on the same day, although apparently there was no statement of what the date of Easter would be.
It took more centuries for the current method of determining the date of Easter to be agreed upon, a method that was worked out by the ancient church of Alexandria (now known as the Coptic Church). After the Western church accepted the reforms of the Gregorian calendar in 1582, while the Eastern churches continued to follow the old Roman or Julian calendar, the two branches of Christianity have been split by the difference in the observance of the date of Easter, although technically, they both follow the same system to compute the date.
In both the East and the West, the churches begin with March 21, the ecclesiastical (or church) equinox. Then, they look for the next full moon, then a Sunday. So–again, in the Western churches–the date of Easter occurs between March 22 (although it last occurred on that date in 1818) and April 25 (last in 1943). In 2008, the date of Easter was March 23, and in 2011, the date of Easter will be April 24.
Therefore, the dates of other church holidays also change. Palm Sunday, a week before Easter, marks the beginning of Holy Week, which includes Maundy Thursday and Good Friday. Ash Wednesday occurs forty-six days before Easter, so that the fast of Lent lasts forty days (since Sundays are never fast days), and Carnival, Shrove Tuesday, or Mardi Gras (fat Tuesday)–no matter what it is called–occurs the day before Ash Wednesday. Ascension Sunday occurs forty days after Easter, and the date of Pentecost is fifty days after the date of Easter.
With all these dates and days, the Quakers (or Society of Friends) seem–as they so often do–to be on the right track, when they decline to celebrate Easter and other holidays (holy days), choosing instead to see every day as holy. At least, if my teacher had been a Quaker, she could have saved herself some embarrassment.
Although I am not a Roman Catholic, I often to turn the online Catholic Encyclopedia (here) for information on topics related to Christianity. You can find more information on many of the words used in this article in that great resource. If you found this article interesting (along the lines of something you always wanted to know, but didn’t ever get around to asking), why not share it with someone else who may find it interesting as well?