With the return of the Christmas season, I like to remind people that so much of what we learn about the holiday may not actually be so. You probably learned that Christians placed Christmas on December 25 to co-opt Saturnalia, the Roman Empire's mid-winter festival, or possibly the Festival of the Unconquered Sun -- Sol Invictus. The theory went that Christians could get the heathen to convert by co-opting the pagan holidays.
There is one problem -- it sounds more convincing than it is. These theories only became popular once comparative religion became trendy after the 18th century. Going back to the earliest Christian church finds evidence that Christmas, though not initially celebrated, had been commemorated well before the Feast of the Unconquered Sun's creation for entirely Christian reasons. In fact, it is possible Emperor Aurelian instituted Sol Invictus on December 25 to combat Christianity's belief that Jesus was born that day.
In Egypt, less than three hundred years after Christ's death, some Christians celebrated his birth in the spring. The earliest references to Christmas come at about 200 A.D., at a time Christians were not incorporating other religious traditions into their own. In fact, Christians at the time were trying very hard to blend in as citizens while avoiding participation in the various pagan festivals and activities. By 300 A.D., many Christians were celebrating Jesus's birth around December 25th. Within 100 years, Christmas was on the calendar record. Christians looked to December because the early church was far more interested in Jesus' death. His death and resurrection is what matters to the Gospel and that was the date the early church focused on.
"Around 200 A.D. Tertullian of Carthage reported the calculation that the 14th of Nisan in the year Jesus died was the equivalent to March 25 in the Roman calendar," reported Andrew McGowan at the Biblical Archaeology Society. That would be the day of Crucifixion. The math from there is rather simple. Nine months later would be December 25. Early church history held as fact that the prophets and martyrs of the church were conceived on the day they died. So if Christ died on March 25, it was also the anniversary of his conception.
Separately, and more directly from the Bible, Luke 1 tell us Zacharias, John the Baptist's father, was in the priestly division of Abijah. Based on a calculation of this and the division of priest in the temple in 70 A.D. when the temple fell, a number of early Church historians presumed Zacharias would have been in the temple in late September or early October. Later historians, however, speculate it would have been June. The Gospel of Luke tells us when Zacharias left the temple, his wife conceived. "In the sixth month the angel Gabriel was sent from God to a city of Galilee named Nazaerth, to a virgin betrothed to a man whose name was Joseph, of the house of David," Luke 1:25-26 notes.
The early church concluded that six months after Zacharias left the temple would be March as Mary's time of conception. Fast forward nine months and again we find ourselves in December. Given the respect held for Tertullian, everything aligned. With the very earliest Church fathers settling on March 25th as Christ's death and believing fully that Christ's death would occur on the anniversary of his conception, the early church reinforced its belief well before there is any written accusation or evidence of the church incorporating Saturnalia or Sol Invictus into its celebrations. It is important to note, however, that most scholars reject setting Christ's birth to Zacharias's temple service because of problems related to really knowing when he was there.
But there are two final points. One can look at all of this and conclude the church fathers got it wrong. But the real question is whether they themselves thought they got it wrong. They were pretty sure they were right. The earliest Christians refused to celebrate birthdays, but by 300 A.D., there was growing evidence the Church noted Christ's birthday around December 25th. Second, the date of Christ's birth is not important. What is important is that He is.