Why do we celebrate Christmas on December 25? There are popular theories that the December 25 dating was a Christian response to the pagans’ feast of Saturnalia or of Sol Invictus, but neither of these theories seems to work out historically.
Saturnalia, an ancient Roman feast, was celebrated on December 17. That later stretched into a week of festivities lasting until the 23rd, but it doesn’t explain why Christmas would be on the 25th.
What about Sol Invictus? According to this theory, the Emperor Aurelian instituted a celebration of the god Sol on December 25, 274 called Dies Natalis Solis Invicti (“Nativity of the Invincible Sun”). But there are serious problems with this theory as well. The University of Alberta’s Steven Hijmans argues that the theory “lacks even the most basic respect for internal logic and cohesion” by imagining that the Romans willingly “downgraded the old and hallowed Roman cults in favor of a new and oriental one” in the 270s, but then fought to preserve this new sun religion against Christianity fifty years later. As with Saturnalia, the Sol Invictus theory poses basic calendar problems as well, since
December 25 was neither a longstanding nor an especially important official feast day of Sol. It is mentioned only in the Calendar of 354 and as far as I can tell the suggestion that it was established by Aurelian [emperor for 270-275] cannot be proven. In fact, there is no firm evidence that this feast of Sol on December 25 antedates the feast of Christmas at all. The traditional feast days of Sol, as recorded in the early imperial fasti, were August 8, August 9, August 28, and December 11.
Although the Emperor Aurelian did introduce agones, athletic contests to be held in Sol’s honor every four years, these were held from October 19 to the 22nd, with the 22nd being (apparently) the highest feast day to Sol.
A century and a half before the first written record of a nativity feast for Sol Invictus, we find Christians citing the 25th of December as the likely day of Jesus’ birth. Their reason for doing so was fascinating. As Cdl. Ratzinger pointed out in Spirit of the Liturgy, “astonishingly, the starting point for dating the birth of Christ was March 25.” That is, Christians didn’t start with focusing on December 25. They began with March 25 and worked from there.
So what was so special about March 25? Tertullian, around the year 197, writes that Christ died on the cross “in the month of March, at the times of the passover, on the eighth day before the calends of April.” The “calends,” the root of our word calendar, is the first day of the month, and so Tertullian’s claim is that Jesus died on the 25th of March. St. Hippolytus of Rome agrees, adding that he was born on December 25:
For the first advent of our Lord in the flesh, when he was born in Bethlehem, was December 25th [eight days before the kalends of January], 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, March 25th [eight days before the kalends of April] Friday, the eighteenth year of Tiberius Caesar, while Rufus and Roubellion were consuls.
That’s from his Commentary on Daniel, dating back to perhaps 204. All of this is well before the as yet unborn Emperor Aurelian is claimed to have introduced Romans to the cult of Sol Invictus. As the University of Birmingham’s Candida Moss explains:
The real reason for the selection of Dec. 25 seems to have been that it is exactly nine months after March 25, the traditional date of Jesus’ crucifixion (which can be inferred from other dates given in the New Testament). As Christians developed the theological idea that Jesus was conceived and crucified on the same date, they set the date of his birth nine months later.
But this still leaves one major question: where did Christians come up with “the theological idea that Jesus was conceived and crucified on the same date”? Some scholars have speculated that it’s connected with Jewish thought (and that may be true), but the evidence points elsewhere. We get a hint at the answer from St. Augustine, who writes in De Trinitate:
For [Jesus] 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 is highlighting a fascinating detail about the Passion narratives in the Gospels that almost all of us miss. Three of the four Gospel writers point out that the tomb in which Jesus was laid was new. St. Matthew tells us that “Joseph took the body, and wrapped it in a clean linen shroud, and laid it in his own new tomb” (27:59). St. Luke describes it as a tomb “where no one had ever yet been laid” (23:53), and St. John calls it “a new tomb where no one had ever been laid” (19:41). Why would that detail matter to the evangelists? Because it showed the tomb as uniquely set aside for God. Hagios, the Greek word for “holy,” refers to something “set apart by (or for) God, holy, sacred.” The tomb is holy, preserved exclusively for Christ.
This is also how the early Christians understood Mary: that she was, both in body and soul, uniquely set apart for God. The last eight chapters of Ezekiel are a prophecy of a coming temple, a prophecy referring not to a physical building, but to the body of Christ (see John 2:18-22; 7:37-39). Around this temple was a gate, and “this gate shall remain shut; it shall not be opened, and no one shall enter by it; for the Lord, the God of Israel, has entered by it; therefore it shall remain shut” (Ezek. 44:2). The early Christians, including Augustine, saw this as an obvious reference to the perpetual virginity of Mary.
That’s not the way many of us read Scripture today. Chances are, we’ve glossed over the details of the temple gate and the virginal tomb without giving them a second thought (assuming we’ve bothered to read Ezekiel 44 and the Passion narratives at all). But until we learn to chew on Scripture the way the early Christians did, their settling on December 25 as the likely nativity of Our Lord will seem arbitrary . . . or we’ll fall victim to discredited theories about Saturnalia and Sol Invictus.