Who knows why Easter is celebrated on different days every year? Probably the majority. And yet... In the 1st century of our era, the resurrection of Christ was celebrated every week, but in the 2nd, disputes on this account had already begun. Therefore, the Council of Nicaea was held, at which it was decided that Easter would be celebrated after March 21, on the Sunday after the full moon. And since this phenomenon always happens at different times, the date of the celebration also varies. Therefore, in order to determine the date of the celebration of Easter, first determine when the moon will be full for the first time after the vernal equinox. And next Sunday will be a holiday.

However, Christians use two different calendars. Orthodox and Greek Catholics follow the Julian calendar. Catholics prefer the Gregorian calendar, according to which spring begins 13 days earlier. That is why Catholic and Orthodox Easter are celebrated on different days, but sometimes both dates coincide.