Does it really matter? It’s important to know.
No historical evidence suggests that Jesus was born on the 25th.
How is this?
First, the Bible says that “shepherd were with their flocks,” and shepherds do not tend their flocks in December. It is too cold and there is not enough light by which to watch them.
Second, the reason David and Mary went to Jerusalem was to register for a Roman census. Roman censi (plural) were not taken in December because it was too cold and the roads were in too poor of conditions to expect people to travel back to their birth-towns.
Also, by comparing Jesus’ birth with John the Baptist’s birth, we discover that Jesus was probably born in late September. Since Elizabeth (John’s mother) was in her sixth month of pregnancy when Jesus was conceived we can determine the approximate time of year Jesus was born. John’s father, Zacharias, was a priest serving in the Jerusalem temple during the course of Abijah, which is in mid-July. Zacharias rushed home and conceived John, who was born nine months after June, or March. Six months later (the difference in age between Jesus and John), Jesus would have been born. In September!
Finally, the early Church made many decisions to help make it easier for converts to Christianity to acclimate to their new faith. One such decision was to celebrate Jesus’ birth on the 25th, which corresponds to the pagan festival of Saturnalia. The winter solstice is the 21st, and that’s the shortest day of the year. The Sun in the sky is present for the least amount of time during the day and is at its lowest in the sky. The Sun has essentially “died.” The Sun stays like that for three days. The “Sun is dead for three days.” The Sun is fixed, at this time, on a constellation called the crux. Crux is Latin for Cross. “The Sun is dead for three days on the cross.” Then, on December 25th, the Sun begins to rise in the sky. Days get longer all the way up until June 25, the Summer Solstice! On December 25th, the Sun is born! It’s a bunch of scattered Christian theology presented in a nice, adaptive package for neohpyte, pagan Christians!