In a few weeks, we will celebrate one of the most significant holidays in Christianity—Easter. This year, Easter falls on April 20th. Last year, it was celebrated on March 31st; in 2026, it will fall on April 5th. Who and how determines these dates?
The calculation process is quite fascinating. The Church determines them using the computus, which ties the celebration to the lunar calendar: it falls on Sundays following the first full moon after the vernal equinox (around March 21st). This is a reason why the date of Easter changes every year.
A 6th-century scholar and monk, Dionysius Exiguus, developed a system to calculate Easter dates for past and future centuries. He even defined the date of the very first Easter—the resurrection of Jesus. According to his system, this would have been on March 25th, 31 AD. Dionysius did not claim that Easter was celebrated precisely on this date but proposed it as part of his broader chronology work, including the Anno Domini era (the AD calendar we use today).
