Most Christian theologians believe that Jesus was actually born in the spring, because the scripture mentions shepherds letting their animals roam in the fields at night. The Christian church probably chose December 25th as the official birth date because of competition with pagan cults, who celebrated the winter solstice on that date.
The problem with combining Christian and pagan traditions was that the winter solstice had traditionally been a time of drunken feasting and revelry, and many Christmas celebrations became similarly festive. Many preachers began to speak out against the celebration of Christmas, and after the Protestant Reformation, Puritans outlawed Christmas altogether..."
- Continued at The Writer's Almanac