Questions of timing

Over the years I have been asked why the date of Easter changes every year. For example, this year Easter is April 4. Next year it is April 24 – the second latest it can be in 50 years. You can find the calendar dates for Easter and other Church year festivals on page 162 in Christian Worship: A Lutheran Hymnal.

The short answer I’ve always given for the date change is that Easter is based on the date of the Jewish Passover celebration which changes based on the lunar cycle. Recently I was asked why the date for the Passover changes if it says in Leviticus: “The LORD's Passover begins at twilight on the fourteenth day of the first month.” (23:5) The question was, how can the date change if it is always celebrated on the fourteenth day of the same month.

I thought that was an excellent question. I wasn’t sure myself, so I went to the Q & A section at wels.net. Here are the answers. I hope they are helpful.

The Jewish religious calendar is a lunisolar calendar. Its months are true lunar months based on lunar cycles of approximately 29 1/2 days, but its year is a solar year of approximately 365 days. Since 12 lunar months are only 354 days, the months would soon drift through the seasons of the year unless adjustments were made. The seasons are kept in line by adding a thirteenth month to the year in seven out of 19 years. This "slack" in the calendar allows Passover to come after Easter sometimes.

Passover is always celebrated on the 15th of the lunar month of Nisan (with the preparation of the lamb on the afternoon of the 14th). As the midpoint of a lunar month, the Passover is always at a full moon. The early church celebrated Easter on the Sunday after the Passover. (Some Eastern Christians celebrated it the same date each year, regardless of the day of the week on which it fell.)

The Western church, which always celebrated Easter on Sunday, eventually began to make its own calculation of Easter, independent of the Jewish calendar, according to the rule: Easter is the first Sunday after the first full moon of spring. Because of the drift in the Jewish calendar, the first full moon of spring can occasionally be the full moon before the full moon of Nisan. Under these circumstances Passover will come after Easter.

There has often been disagreement among different Christian churches about the formula used to calculate the date of Easter. For example, the date of "Russian Easter" may be different than the date of "Western Easter" because the Russian church uses the Julian calendar rather than the Gregorian calendar as the basis for its calculations.

Why isn’t Easter, like Christmas, observed on the same date each year?

It’s because of two decisions made by the early Christians: 1) to celebrate the resurrection on a Sunday and 2) to celebrate it near the time of the Jewish Passover. Since the Passover is observed on the 14th day (full moon) of the first complete month in spring, the believers set the date for Easter as the first Sunday after the first full moon in spring. Setting the date for Easter was important in the development of the church year calendar.