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Biblical Archaeology Review 48:4, Winter 2022

Calculating Christmas

Hippolytus and December 25th

By T.C. Schmidt

Many readers will be familiar with the common refrain that December 25, Christmas, was originally a pagan holiday, perhaps corresponding to the Roman festival of Saturnalia or the feast of the sun god Sol. As the chorus goes, the date was chosen for the birth of Jesus to make Christianity chime with a polytheistic society already attuned to December 25 revelry. But is the old song true?

I myself used to sing this kind of anti-carol, but then, while translating a treatise of Hippolytus of Rome, I came across a passage stating that Jesus was born on December 25.1 Now, Hippolytus was a Christian author who wrote in the early third century A.D., and Saturnalia and the feast of Sol were not celebrated on December 25 that early in Roman history; Saturnalia never was, and the feast of Sol only came to be later. So Hippolytus clearly could not have chosen the date to please pagan sentiments.

This discovery was exciting, yet as scholars have long known, the manuscripts of Hippolytus’s treatise are divergent, with some claiming Jesus was born on December 25, but others giving one or two alternative dates. Because later Christians marked the birth of Jesus on different days in December and January, many have concluded that subsequent scribes must have changed Hippolytus’s original dating. These changes then ultimately contaminated the manuscript tradition, leaving us to sort out the mess. In all likelihood, though, Hippolytus did have in mind an exact date for Jesus’s birth—but was it December 25?

Fortunately, an early Christian artifact shines light on this question. I speak of the famous Statue of Hippolytus, perhaps the oldest extant piece of Christan art that can be precisely dated. This statue is now in the Vatican Library and depicts a figure seated on a chair. On the sides of the chair are extensive inscriptions extracted from the works of Hippolytus and dating to 222 A.D. Intriguingly, in one of the inscriptions Hippolytus states that the “Genesis of Christ” occurred on the Passover of April 2, 2 B.C.

Scholars have typically interpreted the Greek term genesis as referring to the “birth” of Jesus, but in an extensive study I have shown that the word most likely refers to the “conception” of Jesus. This is why the Gospel of Matthew says, “The genesis of Jesus Christ happened in this way: After his mother Mary was betrothed to Joseph, before they came together, she was found with child by the Holy Spirit” (Matthew 1:18, author’s translation).

And this is where we must do a little math. A typical gestational period is, of course, around nine months (a fact recognized already in antiquity), and nine months from April 2 is pretty near to December 25. So Hippolytus could have believed Jesus was born on December 25, but did he actually?

What we need is another good clue. Happily, this can be found in a different work of Hippolytus, one called the Chronicon. In this, Hippolytus makes all sorts of chronological calculations involving the dates of biblical events and personages. Careful examination of these calculations makes clear that Hippolytus believed Jesus was born precisely nine months after March 25, the vernal equinox of the Roman calendar. And naturally, nine months from March 25 is exactly December 25, the Roman winter solstice.2

Though it is not certain that Hippolytus believed that Jesus was born on December 25, it does seem to be the likeliest interpretation of the evidence as a whole. What is more, once we see Hippolytus’s computational thoughts for what they are, we can see other ancient Christians making similar calculations, beginning with Clement of Alexandria (195 A.D.) and continuing on with many other later writers. For they too believed that Jesus was conceived on Passover and was, therefore, born approximately nine months later—albeit with some selecting slightly different dates for his birth.

Was Jesus really born on December 25? The current evidence suggests that Hippolytus did not derive the date of December 25 from pagan celebrations, but that he also does not seem to have drawn on any ancient tradition for the actual birthday of Jesus either. Otherwise, why would he and his fellow early Christians give slightly different dates for Jesus’s birth? As I said, some, like Hippolytus, do give December 25, but others place the date a bit earlier or later in December or January.

It seems then that these various dates for Jesus’s birth were chosen because Hippolytus and others thought that God organized and balanced the cosmos so as to ensure that profound spiritual moments would coincide with important points in the solar and lunar year. In this way, such sacred happenings would be literally spotlighted by the various cycles of the sun and the moon. Hence, Hippolytus and most of his fellow Christian writers believed that the date of creation, the conception of Jesus, and the crucifixion of Jesus (or, in some cases, his resurrection) all occurred on the solar vernal equinox, or the lunar Passover, or both.

The oldest and strongest tradition, however, concerns the date of Jesus’s conception, which all the earliest sources agree occurred on Passover. And this very consistency explains the diversity of calendrical dates for Jesus’s birth. This is because the lunar Passover drifts back and forth between late March and mid-April. Given this, the dates for Jesus’s conception (and his birth nine months later) would differ in proportion to the date which an ancient Christian chose for the Passover of Jesus’s conception—for the ancients had much trouble calculating lunar phases far into the past or future and consequently often arrived at slightly different dates. This is why some ancient Christians give the date for Jesus’s birth in mid-December, others December 25, and still others early January, since all those dates are about nine gestational months removed from when they each thought the Passover of Jesus’s conception happened to occur.

So, if this is how Hippolytus and others settled on the day of Jesus’s birth, where did they get the idea that Jesus was conceived on Passover?

This remains a mystery. They may have derived it from even more ancient traditions or from theological beliefs about how God organized the world. What is clear, however, is that Hippolytus’s choice of December 25 for the birth of Jesus won out. His choice must have been helped by the fact that only in Hippolytus’s theory would Jesus, the light of the world, begin to shine on the winter solstice, the darkest day of the year; and only on this day could the carol truly be sung:

O come, thou Day-Spring come and cheer Our spirits by thine advent here Disperse the gloomy clouds of night And death’s dark shadows put to flight.3