The church in Rome began formally celebrating Christmas on December 25 in 336, during the reign of the emperor Constantine. As Constantine had made Christianity the effective religion of the empire, some have speculated that choosing this date had the political motive of weakening the established pagan celebrations.

Christmas is celebrated to remember the birth of Jesus Christ, who Christians believe is the Son of God. The name 'Christmas' comes from the Mass of Christ (or Jesus). A Mass service (which is sometimes called Communion or Eucharist) is where Christians remember that Jesus died for us and then came back to life.

Christmas, Christian festival celebrating the birth of Jesus. The English term Christmas (“mass on Christ's day”) is of fairly recent origin. The earlier term Yule may have derived from the Germanic jōl or the Anglo-Saxon geōl, which referred to the feast of the winter solstice.

The celebration of Christmas started in Rome about 336 (but it did not become a major Christian festival until the 9th century). Many Christmas traditions, such as decorating trees, started in Germany and later spread to other parts of the world, notably England and the United States.