How wonderful it would be if Our Lord had been born in the age of information technology or even when the public records office issued birth certificates. Alas, the Gospels do not provide such information. Nevertheless, some scriptural detective work can help determine the date of Christ’s birth.
St. Luke related the announcement of the birth of St. John the Baptist to his elderly parents, St. Zechariah and St. Elizabeth. St. Zechariah was a priest of the class of Abijah (Lk 1:5), the eighth class of 24 priestly classes (Neh 12:17). Each class served one week in the temple, twice a year.
Josef Heinrich Friedlieb has established that the priestly class of Abijah would have been on duty during the second week of the Jewish month Tishri, the week of the Day of Atonement or in our calendar, between Sept. 22 and 30. While on duty, the Archangel Gabriel informed Zechariah that he and Elizabeth would have a son (Lk 1:5-24). Thereupon, they conceived John, who after presumably 40 weeks in the womb would have been born at the end of June. For this reason, we celebrate the Nativity of St. John the Baptist June 24.
St. Luke also recorded how the Archangel Gabriel told Mary that Elizabeth was six months pregnant with John (Lk 1:36), which means the Annunciation occurred March 25, as we celebrate. Nine months from March 25, or six months from June 24, renders the birth of Christ at Dec. 25, our Christmas.
On a pious note, would not our Blessed Mother herself have remembered all of these details, especially how she conceived by the Holy Spirit and bore the Savior? Surely. All mothers — including my own — remember these details. Would not the apostles have asked her these questions, at least after the Ascension? Would not St. Luke, who included the details of the Annunciation and Visitation, not have learned them from our Blessed Mother? Pope Benedict in his book Jesus of Nazareth: The Infancy Narratives noted this very point: “Luke indicates from time to time that Mary, the Mother of Jesus, is herself one of his sources, especially when he says in 2:51 that ‘His mother kept all these things in her heart’ (cf. also 2:19) Only she could report the event of the Annunciation, for which there were no human witnesses. … To sum up: What Matthew and Luke set out to do, each in his own way, was not to tell ‘stories’ but to write history, real history that had actually happened, admittedly interpreted and understood in the context of the word of God.” So given the facts of the Gospel, we discover the date of Christmas.
Now if this dating is true, then the early church must have celebrated Christmas Dec. 25. Is there evidence? Admittedly, evidence is sparse because Christianity and the church were persecuted by the Roman Empire until 313, and no one knows how much evidence has been lost. Nevertheless, according to the Liber Pontificalis, Pope St. Telesphorus (125-136) instituted the tradition of celebrating midnight Mass, which means Christmas already was being celebrated. St. Theophilus (AD 115-181), bishop of Caesarea, stated, “We ought to celebrate the birthday of Our Lord on what day soever the 25th of December shall happen.” St. Hippolytus (170-240) mentioned in his Commentary on Daniel that the birth of Christ occurred Dec. 25.
After Constantine legalized Christianity in 313, the church was able to establish universal dates for the celebration of feast days, including Christmas and the Annunciation. As such, evidence shows the celebration of Christmas Dec. 25: Pope Liberius (352-66) celebrated Christmas Mass in Rome; St. Gregory Nazianzus (d. 389) in Constantinople, and St. Ambrose (d. 397) in Milan. Keep in mind that they would not have just “picked a date,” but used the date already accepted by the church.
So what about Christmas being substituted for the pagan holidays? The Romans did celebrate Saturnalia between Dec. 17 and 23, commemorating the winter solstice Dec. 23, but Christmas does not fit that time frame.
What about the “Birthday of the Unconquered Sun” Dec. 25? Emperor Aurelian instituted this celebration in 274 (therefore, after the Christian celebration of Christmas and perhaps to overshadow it). After legalization in 313, Dec. 25 was purged of any pagan notion: For example, an ancient codex of that time marked Dec. 25 as the “Nativity of the Unconquered” (meaning Jesus), not the “Nativity of the Unconquered Sun.” Then again, Emperor Julian the Apostate (reigned 361-63), who had apostatized and wanted to return the empire to paganism, tried to suppress Christmas and ordered the celebration of the Birth of the Unconquered Sun, a decision reversed upon his death. In sum, Christmas was celebrated Dec. 25 prior to any pagan celebration on the same date. (See Taylor Marshall’s The Eternal City: Rome and the Origins of Christianity).
While we can verify the date of Christmas, the most important point is celebrating the birth of Our Lord. Remember “Christmas” is derived from the Old English Cristes Maesse, which means “The Mass of Christ.” This Christmas, may we lift up our hearts at the holy sacrifice of the Mass and receive Our Lord, born again into our souls through the grace of the holy Eucharist.