Scholars attempted to calculate an exact date for the Nativity of the Lord, but it was deemed impossible. (There was/is not enough information available to determine this.) So originally, March 25 was discussed as an appropriate day to celebrate the birth of Christ to coincide with the rebirth of spring. However, other scholars noted that this would be a better day to place Jesus’ conception, as we believe that God becomes incarnate at the moment he is in Mary’s womb.
Therefore, if we add nine months to that date we get … December 25!
Secondarily, many Romans were sun worshipers and celebrated a kind of sun feast day on December 25, while others note a virility god named Mithra with the same birthday. Romans also observed a debaucherous time of year called Saturnalia December 17-23. Thus, celebrating the birth of Christ on December 25 would counter pagan holidays.
In 336, the Emperor Constantine officially named the “birthday of Christ” December 25.
