Easter, the Christian Holiday is a moveable Feast

Easter, the Christian holiday that celebrates the day of the resurrection of Jesus Christ, is a moveable feast, which means that it does not occur on the same date every year. Easter is calculated based on the phases of the moon and the coming of spring.

Determining the Date of Easter:

In 325, A.D., the Council of Nicaea, which agreed upon the principles of Christianity, established a formula for the date of Easter is the Sunday following the paschal full moon, which is the full moon that falls on or after the spring equinox. In practice, that means that Easter is always the first Sunday after the first full moon that falls on or after March 21. Easter can occur as early as March 22 and as late as April 25, depending on when the paschal full moon occurs.

The Significance of the Paschal Full moon:

The Council of Nicaea decided that Easter must always occur on a Sunday because Sunday was the day on which Christ rose from the dead. But why is the paschal full moon used to determine the date of Easter? The answer comes from the Jewish calendar. The Aramaic word “paschal” means “pass over”, which is a reference to the Jewish holiday.

Passover fell on the date of paschal full moon in the Jewish calendar. Jesus Christ was Jewish. His last supper with his disciples was a Passover Seder. It is now called Holy Thursday by Christians and is the Thursday immediately before Easter Sunday. Therefore, the very first Easter Sunday was the Sunday after Passover.

Many Christians erroneously believe that the date of Easter is currently determined by the date of Passover, and so they are surprised when Western Christians sometimes celebrated Easter before the Jewish celebration of Passover.

The paschal full moon can fall on different days in different time zones, which can present a problem when calculating the date of Easter. If people in different time zones were to calculate the date of Easter depending on when they observed the paschal full moon, then that would mean that the date of Easter would be different depending on which time zone they lived in. For that reason, the church does not use the exact date of the paschal full moon but an approximation.

For calculation purposes, the full moon is always set on the 4th day of the lunar month. The lunar month begins with the new moon. For the same reason, the church sets the date of the spring equinox at March 21, even though the actual vernal equinox can occur on March 20. These two approximations allow the church to set a universal date for Easter, regardless of when you observe the paschal full moon in your time zone.