December 25 was the date the Romans marked as the winter solstice, the shortest and darkest day of the year, and the first day in which the days would begin to elongate and the Sun would have a longer presence in the sky.
Christmas played a role in the Arian controversy of the fourth century.
This is not a disagreement over the date of Christmas as such, but rather a preference of which calendar should be used to determine the day that is December 25.
Although it is not known why December 25 became a date of celebration, there are several factors that may have influenced the choice.
Jesus chose to be born on the shortest day of the year for symbolic reasons, according to an early Christmas sermon by Augustine: "Hence it is that He was born on the day which is the shortest in our earthly reckoning and from which subsequent days begin to increase in length.
He, therefore, who bent low and lifted us up chose the shortest day, yet the one whence light begins to increase." Linking Jesus to the Sun was supported by various Biblical passages.