The second piece of evidence, which the proponents of an alternate time for Christmas present, is the fact that the ancient pagans celebrated on December 25 the birth of the God Sun. As a follow-up syllogism, they conclude that Christians adopted December 25 to cover up the pagan feast, ignoring the historical date of his birth. It is, in fact true that many pagan feasts were Christianized during the fourth century and subsequently, which makes this a reasonable claim. Still, this is no proof that the birth of Christ did not take place at some time in December, even if it was not exactly on December 25, and even if the Christians intentionally overlaid the birth of Christ over the pagan feast.
As we look for more evidence, we discover that the feast of Christmas was first celebrated at the beginning of the fourth century, first in Rome (in 336 AD) and subsequently in the Eastern parts of the Empire by the end of the fourth century, where we find a sermon by St. John Chrysostom explaining why celebrating Christmas in December and especially on December 25 is appropriate and has historical proof in the events of the New Testament.
St. Chrysostom, preaching at the end of the fourth century in Antioch, about ten years after the feast of Christmas was established in the East (as he himself informs us), offers a contemporary account of the reasoning behind the choice of December 25 as the day for celebrating the birth of Christ. He is addressing people who disputed the necessity of the feast (as an innovation) and also the time of its celebration.
He does not mention the effort to remove from the Roman calendar the pagan worship of the Sun, but lays out a very distinct biblical explanation. He starts with the time of the Census as mentioned in Luke 2:1-7 and points out that this was the first Census, which happened when Quirinius was governor of Syria. He also points out that whoever wants to know the exact time of the Census can freely search the ancient codices, which are kept in the public libraries of Rome, hinting that the time of the birth of Christ is easily verifiable from the public records. Chrysostom was a trained lawyer of the time with personal knowledge of government records.
He then continues his argument from a biblical perspective, explaining the Jewish tradition of the censing of the Temple in Jerusalem by the high priest, who would enter the Holy of Holies only once a year (Hebrews 9:7; Lev 16:29-34) during the Feast of Tabernacles in September. He points to the Gospel of Luke 1:8-15, when Zacharias was selected to enter the Holy of Holies to offer incense (perhaps there was no high priest that year and the group of Levites, who were on duty at the time selected by lot, according to tradition, the priest who would make the offering in the place of the high priest).
Zacharias entered the Holy of Holies to offer incense and there he had a vision of an angel of the Lord who announced to him the birth of his son, whom he was to call John. Soon after that, Elizabeth, his wife, became pregnant.
Continuing with the biblical narrative, Chrysostom points out that six months later, the angel Gabriel appears to the Virgin Mary and announces to her that she will bear the Son of God and also reveals to her that her cousin Elizabeth is already in her sixth month of pregnancy (Luke 1:30-37).
Chrysostom concludes that, Elizabeth became pregnant in the latter part of September (after the Feast of Tabernacles) and the Virgin Mary became pregnant six months later in the latter part of March. If we count nine months from that time we end up at the latter part of December, which is the time when Jesus was born. Hence, the celebration of Christmas on December 25 is justified.
The fact is that we do not know the exact day of Christ’s birth, but the Christians of the fourth century had calculated the time of his birth and concluded with December as the month. They were much closer to the original event and much closer to the people who had experienced it than any person of today. Their decision was biblically and historically based and it has to be closer to the real day than any modern guess.
It is possible, however, that the decision to establish the celebration of Christmas on December 25 and not on the 20th or the 24th, or whatever date would have been the real date of the birth of Christ, was intentional, aimed at quashing the pagan feast of the God Sun – although Chrysostom is silent about it in his Homily. It is indeed possible that the Christians sought to substitute the celebration of the birth of the God Sun with the birth of the Son of God. This seems to have become one more victory for them against the dwindling pagan religion that worshiped the creation rather than the Creator. They were comfortable that the season of his birth was the right one and December 25 seemed perfect to them.
Hence, for those who have been worried that they might be celebrating Christmas at the wrong time, please enjoy the joyful feast and find comfort in the fact that the Early Christians knew what they were doing when they decided that December 25 it is.