April's full moon decides the date of Easter — here's how it works

The first full moon of spring, known as the Paschal Moon, sets the date for Easter each year.

The first full moon of spring also has a special branding: the Paschal full moon or the Paschal Term — 14 or 15 Nisan on the Jewish Calendar, which also marks Pesach or Passover. Easter is observed on the Sunday after the Paschal Full Moon. So, according to the current ecclesiastical rules, Easter is to be celebrated on April 5.

Interestingly, however, these rules also state that the vernal equinox is fixed on March 21, even though worldwide from the years 2008 through 2103 it will occur no later than March 20. Hence, there can sometimes be discrepancies between the ecclesiastical and astronomical versions for dating Easter. In the year 2038, for instance, the equinox falls on March 20 with a full Moon the next day, so astronomically speaking, Easter should fall on March 28 of that year.