How is the date of Easter determined?

Dear Cecil: How is it determined which date Easter Sunday will fall on each year? Tim F., Washington, D.C.

Cecil replies:

Easter falls on the first Sunday subsequent to the first full moon after the vernal equinox (March 21). Thus, it can occur as early as March 22 and as late as April 25. (If the full moon after the equinox falls on Sunday, Easter follows a week later.)

Originally Easter was celebrated on the same day as the Jewish Passover. Since the Jewish calendar is lunar, Passover can fall on any day of the week, and some Church fathers were distressed that the Lenten fast should end on any day other than a Sunday. They argued about it until the 8th century, when the church officially adopted the procedure we have now.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.