Easter is a moveable feast, meaning it is not fixed in relation to the civil calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the vernal equinox. Ecclesiastically, the equinox is reckoned to be on March 21. The date of Easter therefore varies between March 22 and April 25. Eastern Christianity bases its calculations on the Julian Calendar whose March 21 corresponds, during the twenty-first century, to April 3 in the Gregorian Calendar, in which calendar their celebration of Easter therefore varies between April 4 and May 8.

Easter is linked to the Jewish Passover not only for much of its symbolism but also for its position in the calendar.Relatively newer elements such as the Easter Bunny and Easter egg hunts have become part of the holiday's modern celebrations, and those aspects are often celebrated by many Christians and non-Christians alike. There are also some Christian denominations who do not celebrate Easter.