How is Easter determined each year?
Easter Sunday differs every year and this has to do with the fact that the date of the holiday is based according to the March Equinox. The day ultimately celebrates the Christian belief that Jesus Christ resurrected, although the church usually marks March 21 as the equinox date, per the ecclesiastical calendar, instead of the actual date, which takes place on either March 19, 20 or 21.
The reason for having Easter Sunday decided based on the March Equinox has to do with the Bible, which stated that the death and resurrection of Jesus Christ took place around the time of the Jewish Passover. This event happened on the first Full Moon after the vernal equinox.
As a result, this led to Christians celebrating Easter on different dates, with some churches celebrating Easter at the end of the 2nd century. Meanwhile, others celebrated the day on the Sunday following that one.
The Council of Nicaea decided in 325CE that Easter would take place on the first Sunday following the first Full Moon, which occurred on or after the vernal equinox. Following this decision, the date in which Easter is celebrated varied, depending on the ecclesiastical approximation of March 21 in regards to the equinox.
If the Full Moon is on Sunday, Easter is pushed back by one week to prevent it from landing on the same day as Jewish Passover.
