|A seated marble statue said to depict St. Hippolytus.|
The first clear source for this date is Hippolytus of Rome, a somewhat mysterious figure from antiquity who may have been an anti-pope of the third century AD. He was later regarded as a saint thanks to his copious theological writings. Sadly, only fragments of his works have survived to the present day, but among them is a work in which Hippolytus provides an analysis of the Old Testament Book of Daniel. The earliest notice of Christmas being celebrated on December 25 comes from this work, as follows:
"For the first advent of our Lord in the flesh, when he was born in Bethlehem, eight days before the Kalends of January [that is, December 25], the fourth day [that is, Wednesday], while Augustus was in his forty-second year, but from Adam, five thousand and five hundred years. He suffered in the thirty-third year, eight days before the Kalends of April (that is, March 25), the day of preparation [that is, Friday] the eighteenth year of Tiberius Caesar, while Rufus and Roubellion were Consuls." [Hippolytus of Rome, Commentary on Daniel, written ca. AD 205]
|Dedication page of the Chronography of AD 354.|
VIII kal. Ian. natus Christus in Betleem Iudeae.This appears to corroborate Hippolytus's date above. Interestingly, Hippolytus is also mentioned in this calendar in a list of the Popes with a notice saying: "In that time the exiled bishop Pontianus and the presbyter Hippolytus were deported to Sardinia on the island of Vocina, Severus and Quintianus being consuls [AD 235]."
After about AD 350, overt references to December 25 as the date of Christ's birth are more numerous, particularly in the Greek east where the date seems to have been more variable before that time. Many in the east had celebrated the Nativity on January 6 -- which would later be recognized as the feast of the Epiphany. Saint John Chrysostom, later bishop of Constantinople but at this point a presbyter in Antioch, offers a meditation on preparing for the Nativity in his homily on the feast of St. Philogonios which was celebrated on December 20. Note that John clearly separates the Nativity from the feast of the Epiphany:
A feast is approaching which is the most solemn and awe-inspiring of all feasts. If one were to call it the metropolis of all feasts, one wouldn't be wrong. What is it? The birth of Christ according to the flesh. In this feast the Epiphany, holy Pascha, the Ascension and Pentecost have their beginning and their purpose. For if Christ hadn't been born according to the flesh, he wouldn't have been baptized, which is Epiphany. He wouldn't have been crucified, which is Pascha. He wouldn't have sent the Spirit, which is Pentecost. So from this event, as from some spring, different rivers flow - these feasts of ours are born. [John Chrysostom, On St. Philogonius, delivered December 20, AD 386]In a subsequent homily that same year while still in Antioch, St. John offers evidence for the date by citing official Roman secular records of the census of Augustus mentioned in Sacred Scripture, as follows:
“The 25th day of December has been celebrated from the beginning as the birthday of Christ, and the knowledge of it is now transmitted to us….It is manifest from Scripture that Christ was born at the enrollment or census, and the very day was certain from a written document in the Roman archives….It is lawful for anyone to search these ancient records, publicly deposited at Rome, and there to learn the time of this enrollment.” [John Chrysostom, In Diem Natalem, Migne: Patrologia Graeca, 49, 353-354. Translation taken from Hyde: "The Date of Christ's Birth" in The Living Church, December 31, 1904 p. 319.]It should be noted that several other early Christian writers, including St. Justin Martyr and Tertullian, appealed to these same census records when defending the Christian faith. The records seem to have existed into the 5th century when they were lost after the Goths and Vandals pillaged Rome.
The dating of Christmas to December 25 seems to have been well established in Africa by about this time as well. In his treatise On the Trinity, Saint Augustine of Hippo writes:
For He is believed to have been conceived on the 25th of March, upon which day also He suffered; so the womb of the Virgin, in which He was conceived, where no one of mortals was begotten, corresponds to the new grave in which He was buried, wherein was never man laid, neither before nor since. But He was born, according to tradition, upon December the 25th. [Augustine, On the Trinity, Book IV, Chapter 5, written beginning AD 400, published AD 428]So it is clear that the roots of the December 25 date for Christmas stretch well back into antiquity.
The other common take-down posed at this time of year is that Christmas was artificially dated to December 25 to superimpose a Christian feast on top of a variety of pagan feasts which happened at around the same time, whether it be Saturnalia, or the birthday of Mithras, or the birthday of Sol Invictis, or the birthday of Horus.
This line of attack has been effectively dealt with many times, so rather than regurgitate the same refutation here, I would point you to this summary article here or this humorous video response by our separated brethren entitled: Horus Ruins Christmas. A balanced and very detailed article on this topic, entitled Sol Invictus and Christmas, is also well worth a read.