Christmas is celebrated on a date specified by the church in the western hemisphere. The day of December 25 has passed into tradition as the date of the birth of Christ. This was not always the case. The first Christian communities celebrated Christmas on various dates between January and May (1).
The exact year and date of birth are not mentioned in the Gospels as they contain little information. Since our timing is based on a miscalculation by a sixth-century monk, Dionysius Exiguus, it can be assumed that Christ was born in the year 6 or 7 BCE.
For the first few centuries, the church had to assert itself alongside other religions. One of the strongest competitors was the Persian Mithraskult, which was widespread throughout the Roman Empire in the 3rd and 4th centuries. This cult showed many similarities with Christian rites and ceremonies: purification by baptism, confirmation to combat evil forces, communion and Sunday rest. The cult was based on the existence of a heaven and a hell. When Emperor Aurelian proclaimed the cult of the invincible sun, "Sol invictus," in 274, he fixed the date of the feast on the 25th of December, a few days after the winter solstice, at a time when the days are getting longer and the Night loses its power over the light. In these solemn ceremonies, the followers of Mithraism celebrated the birth of the sun by sacrificing a bull to them (2), and they recognized their god.
The church disliked this practice. Very soon the ecclesiastical writers, basing themselves on a metaphor of the prophet Malachi, (3) equated the undefeated sun of Mithraism with the Sun of righteousness; H. the invincible God of Christ "light of the world". On the basis of this postulate, the ecclesiastical authorities cleaned up the secular customs that they could not abolish by claiming them for the liturgy.
As early as 336, the "Depositio martyrum", the Roman calendar of the martyr's feast, laid the birth of Christ on the "VIII kal. ianuarii, natus Christ in Bethleem ludeae ". (Christ was born in Bethlehem Judea on the eighth day of the January calendar). The date is finally fixed in the Roman chronograph of the year 354 (4).
The Armenian Church is still celebrating Christmas on the 18th of January. Originally, the churches of the East celebrated the festival on January 6 ... Cf. MATHON-BAUDRY-GUILLUY, Catholicism d'here d'aujourd'hui demain, Paris: Letouzey et Ané, 1982, B. 9, col. 1309-1313.
CUMONT F. Les Mystères de Mithra, Brussels: H. Lambertin, 1900, p. 75 ff.
MALEACHI (3:20): "For you who have been faithful to me, the sun will rise on this day ..."
MATHON-BAUDRY-GUILLY, Catholicisem d'here aujourd'hui demain, op.cit., Koll.1309