I dont know if this helps or not?
The oriental Christians for a long time assigned the 6th of January as the date of the advent; and as they supposed his manifestation to the eastern Magi and his nativity were on the same day, they, in reference to both these events, called the day Epiphany. His baptism was also supposed to have taken place on the same day of the year, and hence this feast was a favorite period for administering this ordinance. On the other hand, the western Christians made a distinction; and whilst they celebrated the Epiphany on the 6th of January, fixed the 25th of December for the Nativity. This was said to have been ascertained as the right day by Julian I., who was bishop of Rome from A. D. 337 to 352; but though the authority for this statement may not be the best, it is sufficiently clear that it was not till about the middle of the 4th century that the Western Church set apart the 25th of December as the Festival of the Nativity; and not till a much later period that the Eastern Church fell into the same usage.