Lady’s Day
Here on the Eleventh Day of Christmas, which is either a day for eleven lady’s dancing, or the memorial to Saint John Neumann, allow me to join in the traditional celebration of arguing over the Internets about the pagan origins of Christmas.
Short answer: Bogus. The early Christians were not trying to sneak pagan ceremonies into the early Church. They were more zealous about keeping the faith pure, and as it had been passed along by the Apostles, than any generation since, as far as I can tell. It is a sad commentary on the world that their success in doing so is commonly and routinely insulted by younger denominations, who assume all these early Church Fathers were traitors to the faith rather than martyrs and witnesses to it.
But, on to the scholarly nitpicking! No, it is too much effort. I will merely quote: http://www.churchyear.net/annunciation.html
Scholars are not completely sure whether the date of the Annunciation influenced the date of Christmas, or vice-versa.
Before the Church adopted fixed days of celebration, early Christians speculated on the dates of major events in Jesus’ life. Second-century Latin Christians in Rome and North Africa tried to find the day in which Jesus died. By the time of Tertullian (d. AD 225) they had concluded that he died on Friday, March 25, AD 29 (incidentally, this is an impossibility, since March 25 in the year AD 29 was not a Friday).
How does the day of Jesus’ death relate to the day of his conception?
It comes from the Jewish concept of the “integral age” of the great Jewish prophets. This is the notion that the prophets of Israel died on the same dates as their birth or conception.
Therefore, if Jesus died on March 25, he was also conceived that day. The pseudo-Chrysostomic work de solstitia et aequinoctia conceptionis et nativitatis nostri Iesu Christi et Iohannis Baptistae accepts the same calculation.
St. Augustine mentions it as well. Other ancient Christians believed Jesus was conceived on March 25th for another reason: they believed (based on Jewish calculations of the period) that the creation of the world occurred that day.
Thus, it was fitting that the one who makes us new creations was conceived on the day the world was created.
For more information see here: http://www.ancient-future.net/christmasdate.html. Also see William Tighe, and The Oxford Dictionary of the Christian Church.