Touchstone Magazine published an article by William J. Tighe entitled: “Calculating Christmas — The Story Behind December 25”. He writes:
Many Christians think that Christians celebrate Christ’s birth on December 25th because the church fathers appropriated the date of a pagan festival. Almost no one minds, except for a few groups on the fringes of American Evangelicalism, who seem to think that this makes Christmas itself a pagan festival. But it is perhaps interesting to know that the choice of December 25th is the result of attempts among the earliest Christians to figure out the date of Jesus’ birth based on calendrical calculations that had nothing to do with pagan festivals.
Rather, the pagan festival of the “Birth of the Unconquered Sun” instituted by the Roman Emperor Aurelian on 25 December 274, was almost certainly an attempt to create a pagan alternative to a date that was already of some significance to Roman Christians. Thus the “pagan origins of Christmas” is a myth without historical substance.
The idea that the date was taken from the pagans goes back to two scholars from the late seventeenth and early eighteenth centuries. Paul Ernst Jablonski, a German Protestant, wished to show that the celebration of Christ’s birth on December 25th was one of the many “paganizations” of Christianity that the Church of the fourth century embraced, as one of many “degenerations” that transformed pure apostolic Christianity into Catholicism. Dom Jean Hardouin, a Benedictine monk, tried to show that the Catholic Church adopted pagan festivals for Christian purposes without paganizing the gospel.
In the Julian calendar, created in 45 B.C. under Julius Caesar, the winter solstice fell on December 25th, and it therefore seemed obvious to Jablonski and Hardouin that the day must have had a pagan significance before it had a Christian one. But in fact, the date had no religious significance in the Roman pagan festal calendar before Aurelian’s time, nor did the cult of the sun play a prominent role in Rome before him. . . .
As things actually happened, Aurelian, who ruled from 270 until his assassination in 275, was hostile to Christianity and appears to have promoted the establishment of the festival of the “Birth of the Unconquered Sun” as a device to unify the various pagan cults of the Roman Empire around a commemoration of the annual “rebirth” of the sun. . . .
The evidence indicates, in fact, that the attribution of the date of December 25th was a by-product of attempts to determine when to celebrate Christ’s death and resurrection. . . .
Second-century Latin (Western) Christians in Rome and North Africa appear to have desired to establish the historical date on which the Lord Jesus died. By the time of Tertullian they had concluded that he died on Friday, 25 March 29. . . .
At this point, we have to introduce a belief that seems to have been widespread in Judaism at the time of Christ, but which, as it is nowhere taught in the Bible, has completely fallen from the awareness of Christians. The idea is that of the “integral age” of the great Jewish prophets: the idea that the prophets of Israel died on the same dates as their birth or conception.
This notion is a key factor in understanding how some early Christians came to believe that December 25th is the date of Christ’s birth. The early Christians applied this idea to Jesus, so that March 25th (in the Western church) and April 6th (in the Eastern church) were not only the supposed dates of Christ’s death, but of his conception or birth as well. There is some fleeting evidence that at least some first- and second-century Christians thought of March 25th or April 6th as the date of Christ’s birth, but rather quickly the assignment of March 25th as the date of Christ’s conception prevailed.
It is to this day, commemorated almost universally among Christians as the Feast of the Annunciation (still commonly March 25), when the Archangel Gabriel brought the good tidings of a savior to the Virgin Mary, upon whose acquiescence the Eternal Word of God (“Light of Light, True God of True God, begotten of the Father before all ages”) forthwith became incarnate in her womb. What is the length of pregnancy? Nine months. Add nine months to March 25th and you get December 25th; add it to April 6th and you get January 6th. December 25th is Christmas, and January 6th is Epiphany.
Christmas (December 25th) is a feast of Western Christian origin. In Constantinople it appears to have been introduced in 379 or 380. From a sermon of St. John Chrysostom, at the time a renowned ascetic and preacher in his native Antioch, it appears that the feast was first celebrated there on 25 December 386. From these centers it spread throughout the Christian East, being adopted in Alexandria around 432 and in Jerusalem a century or more later. The Armenians, alone among ancient Christian churches, have never adopted it, and to this day celebrate Christ’s birth, manifestation to the magi, and baptism on January 6th.
Western churches, in turn, gradually adopted the January 6th Epiphany feast from the East, Rome doing so sometime between 366 and 394. But in the West, the feast was generally presented as the commemoration of the visit of the magi to the infant Christ, and as such, it was an important feast, but not one of the most important ones—a striking contrast to its position in the East, where it remains the second most important festival of the church year, second only to Pascha (Easter). . . .
A Christian Feast
Thus, December 25th as the date of the Christ’s birth appears to owe nothing whatsoever to pagan influences upon the practice of the Church during or after Constantine’s time. It is wholly unlikely to have been the actual date of Christ’s birth, but it arose entirely from the efforts of early Latin Christians to determine the historical date of Christ’s death.
And the pagan feast which the Emperor Aurelian instituted on that date in the year 274 was not only an effort to use the winter solstice to make a political statement, but also almost certainly an attempt to give a pagan significance to a date already of importance to Roman Christians. The Christians, in turn, could at a later date re-appropriate the pagan “Birth of the Unconquered Sun” to refer, on the occasion of the birth of Christ, to the rising of the “Sun of Salvation” or the “Sun of Justice.”
You can read Tighe’s entire article here: