Christmas (in old English, Cristes maesse) is a festival celebrated on Dec. 25, commemorating the Incarnation of the Word of God in the birth of Jesus Christ. In the BCP it is also called The Nativity of Our Lord Jesus Christ. In the United States it is also a popular secular holiday.
According to the Philocalian calendar, Christmas was first celebrated in Rome in the year 336. It gradually spread to the churches of the east, which already had a festival on Jan. 6 commemorating the manifestation of God in both the birth and baptism of Jesus. The date, Dec. 25, rests on no historical foundation. It was probably chosen to oppose the feast Natalis Solis Invicti, the birthday of the "Unconquerable Sun God" (Saturn), which took place at the winter solstice to celebrate the birth of "the Sun of Righteousness."
The customs associated with Christmas have developed from many sources. From early days the popular observance of Christmas was marked by the joy and celebration characteristic of the Roman Saturnalia and the pagan festivals which it replaced. It came to include the decoration of houses with greenery and the giving of gifts to children and the poor. In Britain other observances were added including the Yule log and Yule cakes, fir trees, gifts, and greetings. Fires and lights (symbols of warmth and lasting life) and evergreens (symbols of survival) were traditionally associated with both pagan and Christian festivals. Their use developed considerably in England with the importation of German customs and through the influence of the writings of Charles Dickens
In the BCP, Christmas Day is one of the seven principal feasts. The Christmas season lasts twelve days, from Christmas Day until Jan. 5, the day before the Epiphany. The season includes Christmas Day, the First Sunday after Christmas Day, the Holy Name of Our Lord Jesus Christ, and may include the Second Sunday after Christmas Day. In many parishes, the main liturgical celebrations of Christmas take place on Christmas Eve. The BOS includes a variety of resources for use during Christmas, including a form for a Station at a Christmas Crèche, a form for a Christmas Festival of Lessons and Music, and seasonal blessings for use during the Christmas season.