Why we Celebrate Christmas on December 25 (It is NOT Pagan!)

Every year, as autumn leaves give way to winter frost, a familiar conversation emerges around office water coolers and social media feeds: "You know, Christmas is actually a pagan holiday. Christians just took over the Roman festival of Sol Invictus." Perhaps you've heard this claim at a holiday party, seen it in a documentary, or even wondered about it yourself as you hung ornaments on your tree. It's become such common knowledge that many Christians themselves believe it, sometimes feeling a twinge of discomfort about their beloved celebration.

But what if this widely accepted "fact" isn't quite as factual as we've been led to believe? What if the story of December 25th reveals something far more profound about how the early Christians understood the mystery of the Incarnation—and what if that understanding could deepen our own faith today?

 

The Popular Myth and Its Appeal

The conventional narrative goes something like this: Early Christians, wanting to convert pagans, cleverly appropriated the Roman feast of Sol Invictus (the "Unconquered Sun") celebrated on December 25th, or perhaps the winter solstice festivities, and transformed them into a celebration of Christ's birth. This theory, often called the "History of Religions" hypothesis, gained particular traction in the 18th and 19th centuries during the Enlightenment, when scholars were eager to find naturalistic explanations for religious phenomena.

The appeal of this explanation is understandable. It seems to demonstrate religious evolution, cultural borrowing, and strategic missionary adaptation all at once. However, the historical evidence tells a remarkably different story—one that reveals the profound theological reasoning of the early Church.

 

The Historical Timeline: A Surprising Reversal

Here's where things get interesting. The earliest evidence we have for Christians celebrating Christ's birth on December 25th predates the establishment of Sol Invictus as an official Roman feast. The Roman Emperor Aurelian established the feast of Sol Invictus in 274 AD. However, we have evidence of Christians calculating December 25th as Christ's birthday as early as 200–211 AD.

Hippolytus of Rome, writing in his Commentary on Daniel (204 AD), states: "For the first advent of our Lord in the flesh, when he was born in Bethlehem, was December 25th, a Wednesday, while Augustus was in his forty-second year" (Commentary on Daniel 4.23.3). This is roughly 70 years before Aurelian’s establishment of Sol Invictus. Even more intriguingly, some scholars suggest that Aurelian may have chosen December 25th for his sun god precisely because Christians were already celebrating it as a significant date.

But if Christians weren’t borrowing from pagan festivals, how did they arrive at December 25th?

 

The Calculation Theory: A Theological Masterpiece

The answer lies in what scholars call the "Calculation Theory" or "Computation Theory," and it reveals the breathtaking theological sophistication of the early Church. The ancient Christians didn't randomly select a date or steal one from their neighbors—they calculated it based on a profound theological principle rooted in Jewish thought.

In ancient Jewish tradition, there was a belief that important figures died on the same day they were conceived. This concept, known as the "integral age" of the prophets, held that God’s most significant servants entered and left the world on the same date, creating a perfect circle of life.

Early Christians applied this principle to Jesus Christ. They calculated that Jesus died on March 25th (14 Nisan in some calculations of the Jewish calendar converted to the Roman calendar). Following the integral age concept, they reasoned that this must also have been the date of His conception—the moment when "the Word became flesh" ($\text{John 1:14}$). This date became celebrated as the Feast of the Annunciation.

Count nine months forward from March 25th, and where do you arrive? December 25th.

 

Eastern Confirmation: January 6th and the Same Logic

This calculation theory gains even more credibility when we look at the Eastern churches. Eastern Christians, using slightly different calendar calculations, determined that Christ died on April 6th. Using the same theological principle of integral age, they placed His conception on April 6th. Nine months later? January 6th—which Eastern churches originally celebrated as the Nativity and which all Christians still celebrate as Epiphany.

The fact that both Eastern and Western churches independently arrived at their dates using the same theological methodology—but with different calendar calculations—strongly suggests this was indeed the ancient method, not borrowing from pagan sources.

St. Augustine, writing in On the Trinity (c. 399–419 AD), explicitly confirms this calculation method: "For he is believed to have been conceived on the 25th of March, upon which day also he suffered... But he was born, according to tradition, upon December the 25th" (On the Trinity, Book IV, Chapter 5). Augustine treats this not as a recent innovation, but as an established tradition based on theological reasoning about the symmetry of salvation history.

 

The Deep Theology: Light in Darkness

But why does any of this matter beyond historical curiosity? The answer touches the very heart of the Incarnation's meaning.

The early Christians weren't simply picking dates from a calendar; they were making a profound theological statement. By linking Christ's conception to His death, they were declaring that the entire life of Jesus—from the moment of the Annunciation to His crucifixion—was one unified act of redemption.

Moreover, that December 25th falls near the winter solstice is not a borrowing from paganism but a recognition of divine providence. As St. John Chrysostom preached in 386 AD: "They call it the 'Birthday of the Unconquered.' Who indeed is so unconquered as Our Lord? They call it the birthday of the solar disk, but Christ is the Sun of Justice" (Homily on the Nativity).

The early Christians saw in the natural rhythm of creation—darkness giving way to light—a symbol of the spiritual reality proclaimed in John's Gospel: "The light shines in the darkness, and the darkness has not overcome it" ($\text{John 1:5}$). This wasn't syncretism; it was seeing all of creation as speaking of its Creator.

 

Reclaiming the Wonder: What This Means for Us

Understanding the true origins of December 25th offers us several profound insights for our spiritual lives today:

It reminds us that Christianity is not a faith built on borrowed myths or clever marketing strategies, but on deep theological reflection about God’s action in history.

It challenges us to see the liturgical calendar as theological teaching in temporal form. When we celebrate Christmas on December 25th, we’re not just remembering a birthday; we’re proclaiming that Christ’s entire life was a unity of salvific purpose, from conception to resurrection.

It invites us to recover a sense of cosmic Christianity—seeing God’s handiwork not just in Scripture and sacrament, but in the very rhythm of creation. The lengthening days following December 25th become a natural icon of Christ’s words: "I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life" ($\text{John 8:12}$).

As we prepare for Christmas this year, how might this understanding transform our celebration? Here are some practical suggestions:

Meditate on the Annunciation-Christmas Connection: This Advent, spend time contemplating how Mary's "yes" to the angel connects to the child in the manger.

Embrace the Darkness: Let yourself experience the growing darkness of December. Then, as you illuminate your home closer to Christmas, let it be a conscious act of proclaiming Christ as the light no darkness can overcome.

Study and Share: Learn more about the actual history of Christian feasts. When you encounter the "Christmas is pagan" myth, gently share what you've learned—not in a spirit of argument, but as an invitation to discover the beautiful theological reasoning behind the date.

 

Conclusion: An Affirmation of the Date

While the historical arguments against December 25th are persistent and popularly cited, the historical and theological case for this date is far stronger and older than many realize. It is a date anchored not in pagan appropriation, but in the earliest Christian attempts to understand the Incarnation within the framework of salvation history.

The decision by early Christians to affirm December 25th was a powerful theological act. By linking the Conception ($\text{March 25th}$) to the Nativity ($\text{December 25th}$) based on the date of Christ's Passion, they proclaimed a profound truth: Jesus's birth was not an accident of time, but the intentional start of the redemptive mission that would culminate on the Cross. The date itself proclaims the unity of Christ's saving work.

Therefore, we Christians should not only continue to celebrate Christmas on December 25th but should do so with renewed confidence and deeper theological conviction. We are not celebrating a pagan re-run; we are affirming a truth calculated by the Church Fathers nearly two millennia ago: that the Sun of Justice was born on a day when the physical light of the world begins its return, forever marking the moment that God entered the darkness of human history to bring us the Light of Life.

The date of December 25th is a gift of the early Church's wisdom, a calendar marker that makes a magnificent theological claim, and a tradition we should cherish as a brilliant expression of our faith.