We read in Werner Keller's book The Bible as History the following admission:
Doesn't it seem rather strange that the so-called "Christian church" should choose a day to celebrate the Messiah's birth which was identified as the day of the birth of the unconquered sun, the day of the winter solstice, the "shortest day of the year," when the sunlit part of the days start becoming longer again? What does this have to do with the Messiah, anyway? Was Yeshua the Messiah born anywhere near December 25? Keller goes on:
How interesting! How fascinating! As we explore the time for the birth of the Messiah, we find he was born nowhere near December 25, the very date the world has chosen to "celebrate" supposedly, his "birthday"...