 Caitlin Corning identifies four customs that were common to both the Irish and British churches but not used elsewhere in the Christian world.Easter was originally dated according to Hebrew calendar, which tried to place Passover on the first full moon following the Spring equinox but did not always succeed.In his "Life of Constantine", Eusebius records that the First Council of Nicaea (325) decided that all Christians should observe a common date for Easter separate from the Jewish calculations, according to the practice of the bishops of Rome and Alexandria.