Easter weekend is fast approaching, landing on April 9th this year. For years, I wondered why it moved around so much. In addition, when I began to learn more about my faith, I wondered why Easter doesn’t always land during the Jewish Passover. The history behind the floating holiday, and the disconnect from its Jewish roots, is fairly interesting and worth sharing as a part of my series on the history of Lent/Easter traditions.

A little background is necessary for understanding the whole matter. Easter is the celebration of the resurrection of Jesus, which occurred three days after his crucifixion, death, and burial. Jesus and his disciples were all Jews, and the story of Jesus is deeply connected to Judaism, it’s practices, and beliefs. The Bible’s account of what we call Holy Week, Good Friday, and Easter places it during the Jewish Passover celebration in 33 AD. That date was determined by putting the Passover days mentioned in the gospels against the dates of Passover over various years to determine when they lined up.

A short note: Passover is a Jewish feast lasting 7 or 8 days that commemorates the final plague that was visited on Egypt before the Jews gained freedom from slavery. God commanded His people to sacrifice a lamb, eat it, and paint the doorpost of their homes with the lamb’s blood to signify that they were God’s people. The Angel of Death passed over Egypt that night, and the firstborn sons of all the people and livestock without the blood of a lamb, died. The Egyptians finally released the Jewish people from slavery. They commemorate God’s deliverance from their slavery every year with a feast. While the temple still existed, they sacrificed a lamb every year for the event. Jesus’ sacrifice took place because He is God’s Passover sacrifice to save his people from sin and death.

The date for Passover changes every year, because it is determined with the ancient Jewish calendar. Passover starts on the 15th day of the month of Nissan, which is always a full moon. Theoretically, that date is always the vernal equinox. The tricky part is that the Jewish calendar is a lunar calendar, not a solar calendar like the one that is used today. The lunar calendar is shorter and doesn’t line up with ours. This results in variation between the date of Passover from year to year. In addition, because the Jewish calendar isn’t a year long, it has to be adjusted periodically to accommodate the difference. This is a little like our leap year, in which a day is added every 4 years to fix the calendar drift. Only instead of an added day, the Jewish calendar adds a leap month every 3 years. The 3 year adjustment is further impacted by the 19-year metonic cycle, which is the exact cycle of the moon’s repeating pattern of its phases. The effect is a drifting date in relation to the solar calendar. This is part of the reason Easter moves from year to year, as it is still loosely based on the setting of the Passover date, though not the Jewish calendar specifically.

With that bit of background, the question as to why Easter and Passover don’t always coincide rises. The early church debated at length about when to celebrate Easter. There was some discussion of creating a fixed date, but that was ultimately rejected because it was important to remain faithful to the original observation of Passover, which was tied to the meaning of the holiday.

In 325 AD, the Council of Nicaea, which was the first big meeting of the church leadership after Christianity was declared legal by Rome, chose to settle the debate. They opted to separate the observation of Easter from the Jewish version of the lunar calendar for several reasons, not the least of which was that Christians and Jews were not very friendly toward each other and the church didn’t want to rely on the Sanhedrin’s calendar adjustment every 3 years. Instead of relying on the Jewish calendar to determine the Vernal Equinox, the church simply set a date for it. The new standardized date was March 21st. Easter is always on the first Sunday after the first full moon after March 21st (the standardized equinox date that isn’t the actual equinox.) The two typically end up coinciding, though occasionally, the two land farther apart due to the variations in the date for the equinox. Occasionally, Passover and Easter are determined by different full moons.