How Easter Date is Determined

This has been killing me since last week. To me Easter is an April thing, but not this year. So I started asking around and no one had the answer. Then Google came to the rescue:

Definition of Easter Sunday Date
Easter Sunday is the Sunday following the Paschal Full Moon (PFM) date for the year. In June 325 A.D. astronomers approximated astronomical full moon dates for the Christian church, calling them Ecclesiastical Full Moon (EFM) dates. From 326 A.D. the PFM date has always been the EFM date after March 20 (which was the equinox date in 325 A.D.).

How Easter Date is Determined