Origins

Origen, a father of the Christian church, argued against the celebration of birthdays, including the birth of Christ.It is unknown exactly when or why December 25 became associated with Christ's birth. The New Testament does not give a specific date. Sextus Julius Africanus popularized the idea that Christ was born on December 25 in his Chronographiai, a reference book for Christians written in AD 221. This date is nine months after the traditional date of the Incarnation (March 25), now celebrated as the Feast of the Annunciation. March 25 was considered to be the date of the vernal equinox and therefore the creation of Adam; early Christians believed this was also the date Christ was crucified. The Christian idea that Christ was conceived on the same date that he died on the cross is consistent with a Jewish belief that a prophet lived an integral number of years. Thus, the date as a birthdate for Christ is traditional, and is not considered to be his actual date of birth. The mythological aspects of the birth narrative of Christ in the gospels have been interpreted by those who ascribe to the Jesus myth hypothesis such that the figure of Christ is seen as an ahistorical construct of various forms of ancient mythology, and that there was no historical Christ, and thus no birth.

The identification of the birth date of Christ did not at first inspire feasting or celebration. Tertullian does not mention it as a major feast day in the Church of Roman Africa. In 245, the theologian Origen denounced the idea of celebrating Christ's birthday "as if he were a king pharaoh." He contended that only sinners, not saints, celebrated their birthdays

The earliest reference to the celebration of Christmas is in the Calendar of Filocalus, an illuminated manuscript compiled in Rome in 354. In the east, meanwhile, Christians celebrated the birth of Christ as part of Epiphany (January 6), although this festival focused on the baptism of Jesus.

Christmas was promoted in the east as part of the revival of Catholicism following the death of the pro-Arian Emperor Valens at the Battle of Adrianople in 378. The feast was introduced to Constantinople in 379, to Antioch in about 380, and to Alexandria in about 430. Christmas was especially controversial in 4th century Constantinople, being the "fortress of Arianism," as Edward Gibbon described it. The feast disappeared after Gregory of Nazianzus resigned as bishop in 381, although it was reintroduced by John Chrysostom in about 400.The Twelve Days of Christmas are the twelve days from Christmas Day to the Feast of Epiphany on January 6 that encompass the major feasts surrounding the birth of Christ: a week after Christmas Day on January 1 is the Feast of the Naming and Circumcision of Christ (Jesus was a Jew). The naming of Christ is the formal end of the Christmas story in Luke. The Feast of the Epiphany marks the visit of the Magi (wise men) and is the formal end of the Christmas story in Matthew