"The First Advent of our Lord in the flesh occurred when He was born in Bethlehem, was December 25th, a Wednesday, while Augustus was in his forty-second year, which is five thousand and five hundred years from Adam. He suffered in the thirty-third year, March 25th, Friday, the eighteenth year of Tiberius Caesar, while Rufus and Roubellion were Consuls." - Saint Hippolytus of Rome, Commentary on DanielAlso note in the quote above the special significance of March 25, which marks the death of Christ (March 25 was seen to correspond to the Hebrew month Nisan 14 - the traditional date of crucifixion).**
- the Creation date of the World
- the date of the Annunciation and Incarnation of Christ
- the date of the Death of Christ our Savior
“For Christ is believed to have been conceived on the 25th of March, upon which day also he suffered; so the womb of the Virgin, in which he was conceived, where no one of mortals was begotten, corresponds to the new grave in which he was buried, wherein was never man laid, neither before him nor since. But he was born, according to tradition, upon December the 25th.” - Saint Augustine, De trinitate, Book 4, 5.In about A.D. 400, Saint Augustine also noted how the schismatic Donatists celebrated December 25th as the birth of Christ, but that the schismatics refused to celebrate Epiphany on January 6 since they regarded Epiphany as a new feast without a basis in Apostolic Tradition. The Donatist schism originated in A.D. 311 which may indicate that the Latin Church was celebrating a December 25 Christmas (but not a January 6 Epiphany) before A.D. 311.