Many non-Catholics, even some Catholics, have posited that the reason December 25th is the date of Christmas is due to the Catholic Church wishing to celebrate a Christian feast during the time the pagans celebrate the Winter solstice. They are wrong!
The REAL reason is in ancient times it was believed that one's death date is the same date as one's conception date. March 25, 29 AD was one early date they believe was the date of Jesus' crucifixion. Do the math, 9 months later is December 25th.
The date of Christmas is based upon the DEATH of Christ - not due to Catholics wanting to "compete" with pagans for a Winter solstice holiday! Besides, the Winter solstice is December 21st, not the 25th! If they were truly trying to replace the pagan holiday, Christmas would be on December 21st!
Friday, March 25th we celebrate(d) the Solemnity of the Annunciation - when the angel of the Lord announced to Mary that she would be the Mother of God. Again, THIS is why Christmas is on December 25th.
References to some sites who get this wrong:
https://www.historytoday.com/archive/did-romans-invent-christmas (In fairness, while this one makes arguments for pagan origins, it closes with reference to the Annunciation on March 25th, based on concepts from Judaism which links the death of prophets to their conception).
Of course there are many more, but one thing I will say - in doing this search I found many sites which do acknowledge the Annunciation on March 25th as the reason for celebrating the Christ Mass on December 25th. It is encouraging to see some of the ignorance of years past being overcome by objective reporters.