Among parties explaining the mystery the mystery of Christ, outside the Paschal cycle have the holidays of Christmas and Epiphany. There are now two different names: that of December 25, Christmas and January 6, Epiphany. The distinction and coexistence of them dates from late IV and principles of V. s.
At the beginning, in the first half of century IV the two festivals were a unique celebration of Encarnación of the word, because while this mystery is celebrated in the East on January 6 with the name of “Epiphany”, Natalis Domini (the name given in Rome) was held in the West was on December 25.
On Christmas day appears in Rome in the document called Filocaliano chronograph dating back to 336. A liturgical calendar it appears certain that the indication is not a simple historical sample but the fact of a party insofar as it is considered that the other parties are based on December 25.
Outside Rome in Africa and the birth is already witnessed by Optatus of Milevo (360 A.D.) celebrating also the adoration of the Magi with the feast of December 25.
In the East the feast of the birth begins appear at the end of the fourth century, in 380 Gregorio Nacianzeno inserted in Constantinople (In Sancta Lumina, PG 36, 349).
A dyed speech on December 20 by San Juan Crisóstomo, at that time priest of Antioch, informs us that the first time in the year 386 celebrates the birth in that city on December 25 as distinct from the Epiphany (from January 6) party which was a party coming from Rome.
But really the birth of Christ was the 25th of December? According to the tradition that we find in the Treaty Solstitis et aequinoctitis (s. IV) Jesus would be conceived on the same day and month in which would be killed, i.e. March 25; Therefore the birth would fall on December 25.
But this tradition seems is not at the origin of the feast and more like it would be an attempt at explanation on a basis of astrological mysticism very much in vogue at that time.
Another explanation that historically seems more likely is that seen in the celebration of the new Sun, i.e. the Natalis Invicti, as I said then
The worship of the Sun was in boom by the mitracismo and was a last great offensive against Christianity in the 4th century. Thus was a great honor for the emperors of the 3rd century, including Aurelian, who erected a great temple in honor of the Sun in Rome in field Marcio, having as a symbol the Sun, by the great offensive continued under the apostate Aureliano (335). The popular party in the Sun was the winter solstice insofar as it represented the annual victory of the Sun over the darkness and fell on December 25.
The chronograph (354) marks the birth of Christ, on December 25 on the same day as the civil calendar noted Natalis Invicti.
Inspired by Scripture and by the environmental circumstances, the symbolism of light and the Sun as a reference to Christ was very developed and consecrated by Christians. We can cite some biblical texts as Psalm 18 “It has made the Sun his dwelling”, “will resurface for us the Sun of righteousness” (Mal 4: 2), “will come to visit us the Sun, symbol of Christ, and the same pray returned eastward was diffused among Christians at the time which was celebrating the astronomical birth of the Sun, to also present the true Sun” “: Christ.”
St. Jerome wanted to explain that the birth of Christ should be celebrated on December 25 says: “until that day (December 25) growing darkness and since that day decreases the error comes the truth. Today is born our Sun of righteousness”(Sermon, in Anecd. Mared III 2, 297). And maximum San of Turin (half of century IV) says: “in a true and is ‘ right on this day the birth of Christ, commonly known as the new Sun…” Gladly accept this way of speaking because with the birth of the Savior shines not only the salvation of the human race, but also the light of the Sun” (Sermon 2, PL. 57, 537).