Christmas: Why the 25th?

The most common answer to the question of why the 25th of December is accepted as the date of Jesus' birth is that it is the symbolic time of light emerging from darkness, a concept which dates back to pagan times with the festival of Sol Invictus, which is Latin for Unconquered Sun.

There's another explanation, however, which has its roots firmly in the Judeo-Christian tradition. This explanation holds that Jesus was thought to have been crucified on the very day that he had been conceived: March 25th by the Gregorian calendar and April 6th by the Julian calendar.

Therefore, we ascertain the date that Jesus was born by adding nine months: January 6th in the Eastern Orthodox Church, and December 25th in the Western tradition.