Why does Easter move around in the calendar?

Easter and Christmas are both very important Christian holidays, but while families always gather on Dec. 25

in the winter, the annual spring celebration changes drastically each year on our calendars.

Steven Engler, a professor in religious studies at Mount Royal University, says the basic reason the two differ is because Christmas is fixed to a solar calendar, near the winter solstice, and Easter is based on the Jewish lunar calendar.

He said the Last Supper, which according to Christian belief is the final meal Jesus shared with his apostles before his crucifixion, was a Passover feast — which is part of an important Jewish festival.

"So Christians always had Easter right after Passover," he said. "And then at the Council of Nicaea in the fourth century, Christians decided to separate themselves from the timing of the Jews on that, so ever since then Passover and Easter have been independent, but they’re both in the spring."

Engler says the Church decided March 21 is the vernal equinox — or first day of spring — and Easter falls on the first Sunday after the next full moon.

“Spring starts on [March 21] and you wait for the next full moon, and the next Sunday is Easter,” he said.

“That’s why is varies so much. This year it’s later because it sort of took longer to get to that first full moon after the beginning of spring.”

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