Now we move on to establishing the birthday of Christ from Sacred Scripture in two steps. The first step is to use Scripture to determine the birthday of Saint John the Baptist. The next step is using Saint John the Baptist’s birthday as the key for finding Christ’s birthday. We can discover that Christ was born in late December by observing first the time of year in which Saint Luke describes Saint Zacharias in the temple. This provides us with the approximate conception date of Saint John the Baptist. From there we can follow the chronology that Saint Luke gives, and that lands us at the end of December.
Saint Luke reports that Zacharias served in the “course of Abias” (Lk 1:5) which Scripture records as the eighth course among the twenty-four priestly courses (Neh 12:17). Each shift of priests served one week in the temple for two times each year. The course of Abias served during the eighth week and the thirty-second week in the annual cycle.However, when did the cycle of courses begin?
Josef Heinrich Friedlieb has convincingly established that the first priestly course of Jojarib was on duty during the destruction of Jerusalem on the ninth day of the Jewish month of Av.Thus the priestly course of Jojarib was on duty during the second week of Av. Consequently, the priestly course of Abias (the course of Saint Zacharias) was undoubtedly serving during the second week of the Jewish month of Tishri—the very week of the Day of Atonement on the tenth day of Tishri. In our calendar, the Day of Atonement would land anywhere from September 22 to October 8.
Zacharias and Elizabeth conceived John the Baptist immediately after Zacharias served his course. This entails that Saint John the Baptist would have been conceived somewhere around the end of September, placing John’s birth at the end of June, confirming the Catholic Church’s celebration of the Nativity of Saint John the Baptist on June 24.
The second-century Protoevangelium of Saint James also confirms a late September conception of the Baptist since the work depicts Saint Zacharias as High Priest and as entering the Holy of Holies—not merely the holy place with the altar of incense. This is a factual mistake because Zacharias was not the high priest, but one of the chief priests. Still, the Protoevangelium regards Zacharias as a high priest and this associates him with the Day of Atonement, which lands on the tenth day of the Hebrew month of Tishri (roughly the end of our September). Immediately after this entry into the temple and message of the Archangel Gabriel, Zacharias and Elizabeth conceive John the Baptist. Allowing for forty weeks of gestation, this places the birth of John the Baptist at the end of June—once again confirming the Catholic date for the Nativity of Saint John the Baptist on June 24.
The rest of the dating is rather simple. We read that just after the Immaculate Virgin Mary conceived Christ, she went to visit her cousin Elizabeth who was six months pregnant with John the Baptist. This means that John the Baptist was six months older that our Lord Jesus Christ (Lk 1:24-27, 36). If you add six months to June 24 you get December 24-25 as the birthday of Christ. Then, if you subtract nine months from December 25 you get that the Annunciation was March 25. All the dates match up perfectly. So then, if John the Baptist was conceived shortly after the Jewish Day of the Atonement, then the traditional Catholic dates are essentially correct. The birth of Christ would be about or on December 25.
Sacred Tradition also confirms December 25 as the birthday of the Son of God. The source of this ancient tradition is the Blessed Virgin Mary herself. Ask any mother about the birth of her children. She will not only give you the date of the birth, but she will be able to rattle off the time, the location, the weather, the weight of the baby, the length of the baby, and a number of other details. I’m the father of six blessed children, and while I sometimes forget these details—mea maxima culpa—my wife never does. You see, mothers never forget the details surrounding the births of their babies.
Now ask yourself: Would the Blessed Virgin Mary ever forget the birth of her Son Jesus Christ who was conceived without human seed, proclaimed by angels, born in a miraculous way, and visited by Magi? She knew from the moment of His incarnation in her stainless womb that He was the Son of God and Messiah. Would she ever forget that day?
Next, ask yourself: Would the Apostles be interested in hearing Mary tell the story? Of course they would. Do you think the holy Apostle who wrote, “And the Word was made flesh,” was not interested in the minute details of His birth? Even when I walk around with our seven-month-old son, people always ask “How old is he?” or “When was he born?” Don’t you think people asked this question of Mary?
So the exact birth date (December 25) and the time (midnight) would have been known in the first century. Moreover, the Apostles would have asked about it and would have, no doubt, commemorated the blessed event that both Saint Matthew and Saint Luke chronicle for us. In summary, it is completely reasonable to state that the early Christians both knew and commemorated the birth of Christ. Their source would have been His Immaculate Mother.
Further testimony reveals that the Church Fathers claimed December 25 as the Birthday of Christ prior to the conversion of Constantine and the Roman Empire. The earliest record of this is that Pope Saint Telesphorus (reigned A.D. 126-137) instituted the tradition of Midnight Mass on Christmas Eve. Although the Liber Pontificalis does not give us the date of Christmas, it assumes that the Pope was already celebrating Christmas and that a Mass at midnight was added. During this time, we also read the following words of Theophilus (A.D. 115-181), Catholic bishop of Caesarea in Palestine: “We ought to celebrate the birthday of Our Lord on what day soever the 25th of December shall happen.”
