Marivhon knows something about that.

In 325 AD Constantine called the first Council of Nicea to resolve controversy and establish Christian orthodoxy. The Council established the Unity of the Holy Trinity, the date of Christmas and the date of Easter. Constantine built the Church of the Nativity in Bethlehem, one of the oldest continually operating churches in the world. Also in 325 he declared December 25th to be an Immovable Feast for the whole Roman Empire. The bishop of Rome may have accepted December 25th as the date of birth of Jesus Christ as early as 320 AD, but careful analysis by Catholic scholarship can only establish that it was some time before 354 AD.

Sorry just bored waiting for Ed to Post.