Easter most generally falls on the first Sunday following the first full moon following the vernal equinox. The 2019 vernal equinox came on March 20 at 21:58 UTC. The full moon crested less than four hours later, on March 21 at 1:43 UTC. So why isn’t this Sunday Easter?
The reason is that, by ecclesiastical rules, the equinox is fixed on March 21. That means this week’s full moon did not take place after the equinox, even though, according to astronomy, it did. The upshot is that 2019’s Easter Sunday will fall on April 21.
Bottom line: Easter generally falls on the 1st Sunday following the 1st full moon following the vernal equinox. By ecclesiastical rules, the equinox is fixed on March 21. That means this week’s full moon did not take place after the equinox, even though, according to astronomy, it did. The upshot is that 2019’s Easter Sunday will fall on April 21. — earthsky.org
