Easter is the oldest festival in the Christian tradition. By the time Egeria (c. 380 CE) had travelled to Jerusalem for Holy Week, it was well established and shared by many who made a pilgrimage to the Holy Land.

The First Council of Nicaea in 325 CE, which brought together bishops from around the Mediterranean, including St. Nicholas of Myra (yes, THAT St. Nicholas), decided that Easter would be celebrated on the first Sunday after the first full moon after the first day of Spring.