Christmas (Old English: Crīstesmæsse, meaning "Christ's Mass") is an annual commemoration of the birth of Jesus Christ and a widely observed holiday, celebrated generally on December 25 by billions of people around the world.A feast central to the Christian liturgical year, it closes the Advent season and initiates the twelve days of Christmastide, which ends after the twelfth night Christmas is a civil holiday in many of the world's nations, is celebrated by an increasing number of non-Christians and is an integral part of the Christmas and holiday season.