Christmas has historically been observed primarily by Christians as a religious festival celebrating the birth of Jesus Christ, whom they believe is the Son of God

. The earliest recorded celebration of Christmas on December 25th dates back to 336 AD in Rome during the reign of Emperor Constantine, the first Christian Roman Emperor

. This date was likely chosen to coincide with existing Roman festivals such as the birthday of Sol Invictus, aligning Christian celebrations with the winter solstice

. Over time, Christmas observance spread throughout the Christian world, with different traditions and dates emerging. For example, many Western Christian denominations (Catholics and Protestants) celebrate Christmas on December 24-25 according to the Gregorian calendar, while many Eastern Orthodox Christians observe it on January 6-7 based on the Julian calendar

. Armenians traditionally celebrate Christmas on January 6, combining the Nativity and Epiphany celebrations

. Beyond religious observance, Christmas has also become a widely celebrated secular family holiday observed by many non-Christians around the world

. The holiday includes various cultural traditions such as gift-giving, feasting, caroling, and festive decorations, evolving significantly from its original religious roots

. In summary, Christmas was first observed by early Christians in the 2nd to 4th centuries, formally established on December 25th in the 4th century, and is now celebrated by Christians globally as well as by many non-Christians as a cultural holiday