Why December 25th?

On his blog, Catholic and Enjoying It!, Mark Shea discusses the history of Christmas and the December 25th date. Did you know that records of Christians associating Jesus' birth with December 25th are decades older than any records concerning a pagan feast on that day? So the common "knowledge" that Christians co-opted a Roman Feast Day and turned it into Christmas is wrong. That's interesting.

This is even more interesting:

There was agitation in the early Church concerning, not Jesus' birthday, but the day upon which the historical Good Friday and Easter fell. It finally ended up that, in the Eastern Church, the tradition focused on April 6 as the date for the original Good Friday, while in the Western Church it was widely held that the date was March 25. Why does this matter? Tighe continues:

'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 and April 6th 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, 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.' (emphasis mine)