Why Christmas is Celebrated on December 25

The Gospel reading for today's Mass, on the fourth Sunday of Advent, is on the Annunciation. And a timely reading it is, too, because it provides an answer to the questions of --

Why is Christmas on December 25? Do we really know that that is the day when Jesus was born?


It turns out that the fixing of Christmas Day on December 25 is not an arbitrary decision, nor is it based on the widespread modern belief that the date was picked in order to displace the celebration of a pagan festival on that date. Rather, the date of Jesus' birth was determined by reference to Jesus' conception which, in turn, was calculated by determining His crucifixion and death.

Now, if you subtract nine months from December 25, you get March 25, the Feast of the Annunciation of the Lord. On that day, the Church reflects upon Mary's fiat, "Behold, I am the handmaid of the Lord; let it be done unto me acccording to your word," and upon the Incarnation, the mystery of God coming down from heaven and merging Himself with Man, making Himself small and becoming flesh in the temple and virgin womb of Mary the Immaculate.

So, the question presents itself --
Why do we celebrate the Annunciation on March 25?

Well, that date was fixed in ancient tradition and it is based upon a widespread belief in Judaism at the time of Christ that the prophets of Israel died on the same dates as their birth or conception. By the time of Tertullian, scholars researching the various dates of Passover had concluded that Jesus died on the Cross on March 25. Wrote St. Augustine,

"He is believed to have been conceived on the 25th of March, upon which day also He suffered; so the womb of the Virgin, in which He was conceived, where no one of mortals was begotten, corresponds to the new grave in which He was buried, wherein was never man laid, neither before nor since." (On the Trinity, Book IV, Chapter 5).

Additionally, some Jewish scholars had calculated that the date of Creation was March 25, and it made sense to believe that, since a new creation began upon the Incarnation, Jesus was conceived on the same day as the first creation.

Hence, the tradition arose that, because He was crucified on March 25 and the universe was created on that date, Jesus was conceived on March 25. The day that Mary took her Son's Body into her arms beneath the Cross is the same day that she had taken His Body into her womb at the Annunciation.

And if you add nine months to the date of conception, March 25, you get . . . December 25, Christmas Day.

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See also: Andrew McGowan, How December 25 Became Christmas
William J. Tighe, Calculating Christmas
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