Why is Easter on a different date each year

It may seem relatively natural to many that Easter should indeed be a set accepted date for the Christian celebration of the resurrection of Jesus, as well as the landmark for many other religious festivals. So why is it that the date changes every year? Why is it so hard to keep track of when Easter will be celebrated? In fact, Easter Sunday can fall anywhere between March 22nd and April 25th, which is a span of 4 weeks difference. It’s also been noted that eastern orthodox churches seem to celebrate Easter on a different date to western churches.

In western Christian beliefs, Easter is celebrated on the first Sunday that follows the Paschal Full Moon date of the year. Essentially, this means that Easter is always celebrated on the first Sunday immediately following the first full moon of spring (“the vernal equinox”). However, this thinking changed when western churches decided to put a more formal system into place for determining the date of Easter. In actuality, the date of the Paschal full moon is not determined by lunar events but instead by historical tables. Astronomers approximated the dates of the full moon in future years and the Christian church used these dates to form their calendar of events. Although it has been modified slightly over the years, the 1583 AD table for determining full moon dates, and therefore Christian festival dates, has remained largely the same and has now been permanently established. As a result of this, the Easter Holiday is celebrated anywhere between March 22nd and April 25th each year. The Paschal Full Moon date can vary by up to two days from the actual full moon date.

Western churches typically used the Gregorian calendar to calculate religious festivals, whereas Eastern churches used the Julian calendar which can account for the divide in festival dates between these two hemispheres. While both churches may celebrate Easter on the same day this is a very rare occurrence and a result of these two calendars “overlapping” for this purpose. In both the Gregorian and Julian calendars Easter Sunday is not on a fixed date each year, and is instead based on a lunar system much like the Hebrew calendar. In addition to this, the Eastern churches also have one other major difference to the calculation of the date of Easter. Whereas in Western churches the calculations are based on the Paschal full moon, in eastern churches they use the actual dates of the full moon. While the fact that they use actual full moon dates could mean the calculations are more accurate than western churches, the Julian calendar itself is considered much less accurate than the Gregorian calendar. This further complicates the whole matter and further church legislation in the east has been implemented to ensure the festival does not fall out of line with the vernal equinox, keeping the holiday from being celebrated before April 3rd. It is also necessary to ensure Easter is celebrated after the Jewish Passover holiday, as the death, burial and resurrection of Christ occurred after this celebration.