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.
There were two temples of the sun in Rome, one of which (maintained by the clan into which Aurelian was born or adopted) celebrated its dedication festival on August 9th, the other of which celebrated its dedication festival on August 28th. But both of these cults fell into neglect in the second century, when eastern cults of the sun, such as Mithraism, began to win a following in Rome. And in any case, none of these cults, old or new, had festivals associated with solstices or equinoxes.
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. He led an empire that appeared to be collapsing in the face of internal unrest, rebellions in the provinces, economic decay, and repeated attacks from German tribes to the north and the Persian Empire to the east.
In creating the new feast, he intended the beginning of the lengthening of the daylight, and the arresting of the lengthening of darkness, on December 25th to be a symbol of the hoped-for “rebirth,” or perpetual rejuvenation, of the Roman Empire, resulting from the maintenance of the worship of the gods whose tutelage (the Romans thought) had brought Rome to greatness and world-rule. If it co-opted the Christian celebration, so much the better.
A By-Product
It is true that the first evidence of Christians celebrating December 25th as the date of the Lord’s nativity comes from Rome some years after Aurelian, in A.D. 336, but there is evidence from both the Greek East and the Latin West that Christians attempted to figure out the date of Christ’s birth long before they began to celebrate it liturgically, even in the second and third centuries. 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 his death and resurrection.
From:
http://tinyurl.com/c92wm