And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan.
And straightway coming up out of the water, he saw the heavens opened, and the Spirit like a dove descending upon him:
And there came a voice from heaven, saying, Thou art my beloved Son, in whom I am well pleased.

The day the Holy Spirit descended upon Jesus used to be a major Christian holiday.  Why that changed, I don't know, but it should not have.  This is far more important than the day Jesus was born as a physical being.