I remember reading as a teen a very detailed newspaper article on how the date of December 25 as the birthday of Christ was a Medieval tradition. That is, there was some kind of important pagan celebration around the time of the winter solstice, and the church simply tacked the celebration of Christ’s birth onto that as a way of coopting the pagans.
But it is well established that the church began using December 25 as the birth of Christ a little after the year 300. This was well before the Medieval period. So what was all that stuff about the date coming from a Medieval tradition?
It was simply stuff and nonsense. Anyone who spent a half hour in an average public library would realize the tradition was ancient, not Medieval. Looking back on the matter, the article was as a subtle attack on Christianity. That is, if the central truths of the faith are just Christianized versions of pagan religions, there is nothing special or uniquely true about Christianity. But the facts were made up.
And the attack would not work, anyway. Christmas may be a highly visible part of Christian practice, but it is not a part of Christian belief. That is, the Bible does not give us a date for Christ’s birth, so deconstructing December 25 does not touch the substance of Christianity.
Now that the knowledge that December 25 is an ancient tradition is widespread, the attempt to deconstruct the date takes a different but familiar angle. The ancient Romans had a festival called Saturnalia around the same time. It originally started on December 17 and later expanded through December 23. So we are assured that the church made up the date of December 25 to coopt the pagan celebration.
Obviously, that is not a match. If these people who want to assert a cynical motive for celebrating on December 25 are going to have the attitude that “close” counts, they ruin their own argument. The Romans had so many feasts and holy days, one could almost choose a date at random and either match one of those dates or be close. The argument defeats itself.
More importantly, there are no ancient Christian writings that said, “The Romans are being gluttons, drunkards, and gamblers during Saturnalia, so let us say that Christ was born close to one of those days, because that will help us convert people to Christianity.” Nothing even close.
The church at that time had their own reason for choosing that date, and it sounds odd to modern ears. They decided that a martyr died on the date of his conception. After making a nice calculation for Easter in the relevant year, they added nine months and came up with December 25.
If you want to say this sounds as odd as the Medieval winter solstice and the Roman Saturnalia stories, go ahead. But this was based on what some early Christians believed, not made-up stories of Christians trying to take pagan celebrations and making them their own.
A more biblical/historical method involves noting that Jesus was conceived six months after John the Baptist was, and that John the Baptist was conceived right after his father performed a certain priestly ceremony, as recorded in the Gospel according to Luke. Historians then try to figure out when that father’s priestly division was on duty. They tie this together and come up with Jesus being born in December.
However, that historical calculation can be and has been disputed, so we are left with no certain answer.
But, as was stated above, disputes about the date of the birth of Christ do not strike at the Christian faith. Christians tend to be comfortable celebrating Jesus’ birth on December 25. But it has nothing to do with a cynical ploy on the part of the church to tag along with pagan celebrations. The cynicism is in the minds of people who make such assertions, weak and baseless as they are.