I agree with Zero. Christmas in December is more fitting. Not all Christians celebrate Christmas on December 25th. Some Eastern Orthodox celebrate in it January. Even though it's the same as Mithra, we are not celebrating his birthday. The reason why most Christians celebrate it in Winter/December is due to the Christian calendar. Although sects of Christianity vary, certain things were just done a certain way. Bottom line we are just acknowledging the birth of Christ, which is what Christmas is (and should be) all about.