World History

John the Baptist was born in the Spring, and Luke says Jesus was born six months later.

Shepherds didn't keep their sheep in the field in late December. They were normally in before October.

Other things, such as the time of tax collection, and a pregnant woman being put outside in the dead of winter, also point to Fall.

Couple this with Church habit of Christianizing pagan holidays (it was a good idea), and the possibility of coincidence between the Dec 25 celebration date for the birth of Jesus and various Winter Solstice related festivities seems less likely.