Why is Easter always on a different Sunday?

New York – Christmas is always Dec. 25, Independence Day is always July 4, Mother’s Day is the second Sunday of May, but why you’ll have to always check the calendar for Easter?

Easter is a Christian festivity that marks the resurrection of Jesus. It always falls on a Sunday during March or April. To understand why, you have to look skyward. “The date of Easter is determined by the moon. Easter always falls on the first Sunday after the first full moon after the vernal equinox,” Kim Mandelkow, director of the Office for Worship with the Archdiocese of Milwaukee, said.

This year, the first full moon after the vernal equinox is on Saturday, April 16, putting this Easter Sunday on April 17. April’s full moon is sometimes referred to as the Paschal Moon because of its significance to Easter – ‘paschal’ is defined as relating to Easter or the Jewish Passover. “The moon is not regular,” Father Martin Schlag, a professor and chair of Catholic social thought at the University of St. Thomas in Minnesota, explains. “It doesn’t follow the solar calendar, but it has its own lunar calendar that varies every year.”

According to Mandelkow, if the first full moon fell on a Sunday, Easter Sunday would be pushed back a week.

According to data from the U.S. Census Bureau, because Easter is dependent on the vernal equinox, it can fall anywhere from March 22 to April 25. Having Easter on either of those days, though, is relatively rare.

Next year, we’ll have an earlier Easter on April 9.