I have myself accepted the argument of Christ’s birth being linked to December 25th due to paganism. So much so, that for a time, my family didn’t celebrate Christmas at all–it being a pagan holiday (in our minds).
The most loudly touted theory about the origins of the Christmas date(s) is that it was borrowed from pagan celebrations. The Romans had their mid-winter Saturnalia festival in late December; barbarian peoples of northern and western Europe kept holidays at similar times. To top it off, in 274 C.E., the Roman emperor Aurelian established a feast of the birth of Sol Invictus (the Unconquered Sun), on December 25. Christmas, the argument goes, is really a spin-off from these pagan solar festivals. According to this theory, early Christians deliberately chose these dates to encourage the spread of Christmas and Christianity throughout the Roman world: If Christmas looked like a pagan holiday, more pagans would be open to both the holiday and the God whose birth it celebrated.
However, I have since reconsidered this argument. My family celebrates Christmas, rejecting its supposed pagan connections for more Biblical arguments as to why the people of God should celebrate their delivery from sin, death, hell, and Satan through Jesus Christ. And so, the following discussion is of particular interest to me:
Around 200 C.E. Tertullian of Carthage reported the calculation that the 14th of Nisan (the day of the crucifixion according to the Gospel of John) in the year Jesus died was equivalent to March 25 in the Roman (solar) calendar. March 25 is, of course, nine months before December 25; it was later recognized as the Feast of the Annunciation—the commemoration of Jesus’ conception. Thus, Jesus was believed to have been conceived and crucified on the same day of the year. Exactly nine months later, Jesus was born, on December 25.
I’m not sure it matters how accurate our dating is, as to whether or not we celebrate victory in Christ. But it is always a point of discussion. So, if you’d like to read more of the argument, you can do so at Biblical Archaeology Review’s How December 25th Became Christmas.