He actually was not born on December 25th, I get where youre coming from though. One of the reason it wasnt december is because the sheperds were out with their flock at night when Jesus was born. Why would sheperds be out in the cold with their flock instead of indoors? Granted people might argue theres much difference between todays winter weather in Bethlehem than about 2,015 years ago in Bethlehem but it would still be below 60 at night right? So, we estimate he was born in the Hebrew month of Ethanim (September-October). This month because he was approximately born 6 months after his relative, John the Baptizer.