Christmas was first celebrated as a religious event on December 25 in 352 AD.
Nobody knows the exact tdate when - or in what year - Jesus was born. And it really didn't matter back in those first centuries. Birthdays were less important than remembering the day when someone died.
In fact, the early Christians often celebrated the birth of Jesus on January 6. During the second century, five dates in three different months (including December 25) were considered as possible birth dates for Jesus.
Finally, in the fourth century, Pope Julius I and other Church leaders specified Decmber 25 as the official date for the birth of jesus - to replace the Roman holiday celebrating the birthday of the Sun God, and the return of longers days of sunlight.
The date was accepted by the universal Church in the fifth century.
- Little Blue Book, Diocese of Saginaw