GUEST is correct that the date of Christmas is arbitrary. The actual date of Christ's birth is not known and may properly be celebrated at any time from an historical perspective. Christians begain a common celebration in the fourth century A.D. when the Church set December 25 as the date to be celebrated. Since that was prior to the Great Schism of 1054, both the Roman and Eastern Orthodox Churches celebrate on December 25.

The Greek Orthodox Church uses the New Calendar so their observance coincides with December 25 on the modern (Gregorian) calendar. There are a few “Old Calendar” Orthodox Churches left and most of them originate in Russia and Eastern Europe.

      - Mark