What is the X in X-mas?
The return of Jesus, prophesied in the New Testament, to judge the living and the dead and bring about the final triumph of good over evil. The writings of the Apostles in the New Testament express the belief that the Second Coming will happen soon and suggest that it may happen within a generation of their own time. (See Judgment Day.)
Note: Several Christian denominations, such as the Seventh-Day Adventists and the Jehovah's Witnesses, are founded on a similar belief about the imminence of Jesus' return.