In Orthodoxy, the status of Easter as the main holiday reflects the words “holiday celebrations and celebrations of festivities.” The church celebration of Easter lasts 40 days.
In the first centuries of Christianity, various communities celebrated Easter at different times. In the East, in Asia Minor, it was celebrated on the 14th day of the month of Nisan (March-April), no matter what day of the week this number occurred. The Western Church celebrated Easter on the first Sunday after the spring full moon.
At the First Ecumenical Council in 325 it was decided to celebrate Easter everywhere at the same time in the Alexandria Easter. This continued until the 16th century, when the unity of Western and Eastern Christians in the celebration of Easter and other holidays was violated by the calendar reform of Pope Gregory XIII.
The Orthodox Church determines the date of the celebration of the Passover according to the Alexandrian Easter: the feast must be on the Sunday after the Jewish Passover, after the full moon and after the vernal equinox.