Why “Xmas”? Because if you closely research the accounts in the Gospels, there is no Christ in December 25. The weight of the evidence is extremely strong for Jesus having been born either on the Feast of Trumpets or some other day related to the Feast of Tabernacles.
There is very little evidence that Jesus was born on December 25. Where people raise it, they never give any due consideration to His birth during the Holy Days in the Fall. And they never give any weight to how December 25 falls suspiciously close to the winter solstice. In short, what I see are very strained attempts to justify observing something that they just really want to observe for other reasons.
Then there is the issue of the vast number of opportunities that the text of the New Testament gives to mention how to celebrate the birth of Our Lord, but there is not a single passage. The early Church did not observe it.
For my part, I am trying to observe the faith that was “once delivered” without adding to it or detracting from it. I am no more interested in what new thing some “early church father” may have added hundreds of years after Jesus conveyed the body of knowledge to His Disciples than I am interested in what Justice Ginsburg may have added to the Constitution hundreds of years after it was debated and ratified.
I don’t fault people for liking Xmas. There is a lot of family and personal focus on it. It takes a lot of courage to break from that sufficiently to fully evaluate all the evidence. But as Jesus said, the truth will set you free.
There was in the days of Herod, the king of Judea, a certain priest named Zachariah, of the course of Abia: and his wife was of the daughters of Aaron, and her name Elizabeth. And they were both just before God, walking in all the commandments and justifications of the Lord without blame. And they had no son, for that Elizabeth was barren: and they both were well advanced in years. And it came to pass, when he executed the priestly function in the order of his course before God, according to the custom of the priestly office, it was his lot to offer incense, going into the temple of the Lord.
This practice would have been carried out on the Day of Atonement, which would take place sometime between mid-September and mid-October by the Gregorian calendar.
From Luke 1:11-15 ...
And there appeared to him an angel of the Lord, standing on the right side of the altar of incense. And Zachariah seeing him, was troubled: and fear fell upon him. But the angel said to him: Fear not, Zachariah, for thy prayer is heard: and thy wife Elizabeth shall bear thee a son. And thou shalt call his name John. And thou shalt have joy and gladness: and many shall rejoice in his nativity. For he shall be great before the Lord and shall drink no wine nor strong drink: and he shall be filled with the Holy Ghost, even from his mother's womb.
So at some point in September or October that year, Zachariah is told that his wife Elizabeth will conceive a child who would be John the Baptist.
The Annunciation is then described in the passages starting with Luke 1:26, when the angel Gabriel visits Mary to announce that she will give birth to Jesus Christ. This is described as taking place in Elizabeth's "sixth month," at which point Mary goes and visits her. So this visit would have taken place sometime between mid-March and mid-April of the following year.
Assuming Mary carried Jesus to full term, she would have given birth to Him between mid-December and mid-January. December 25th fits right into this timeline.