What is the Reason Behind Christmas Falling on December 25?

Every December, Christians come together to celebrate Jesus’s birth. However, with no birth certificate or official record confirming his exact birthdate, December 25 appears to be a random day for all of our Christmas traditions. So, how did the early Christians settle on this particular date?

When Exactly Was Jesus Born?

The Bible doesn’t specify the month or even the season of Jesus’s birth, so historians have turned to other clues for an estimate. The shepherds tending sheep in the Nativity story are often cited as evidence that Jesus was more likely born in the spring. Others argue that Israel's mild winter temperatures allow sheep to graze, even in December. According to Slate, it's also possible that sheep set aside for religious sacrifices were given the freedom to graze, regardless of the cold nights.

One clue specifically pointing to December 25 comes from the story of Mary’s cousin Elizabeth, who, after years of childlessness, was told by the angel Gabriel that she would have a son. Elizabeth’s husband, Zacharias, was burning incense in the temple when Gabriel appeared to announce the good news. Early Christians deduced that Zacharias was likely serving in the temple during Yom Kippur, which they believed always occurred on September 24 (though it actually shifts annually). Adding nine months to this date brings us to June 24, which became the feast day and birthday of John the Baptist. Since Gabriel told Mary she was pregnant with Jesus when Elizabeth was six months along, this places Jesus’s conception in late March and his birth around December 25, specifically on the night of December 24 or early December 25.

Another hypothesis suggests that December 25 was chosen based on an ancient Jewish belief that prophets die on the same day they were born. Theologians like Tertullian and Hippolytus in the 3rd century CE linked Jesus’s crucifixion to March 25, around Passover. However, Sextus Julius Africanus focused not on Jesus’s birth but on his earthly mission, believing both Jesus’s death and conception occurred on March 25, making his birth fall on December 25 [PDF].

The Origins of Christmas

Even if Zacharias was indeed in the temple on September 24, Gabriel visited Mary six months later, and Jesus was born exactly on his due date, it remains possible that the celebration of Christmas on December 25 has an entirely different origin.

In the 3rd century, while Christians were devoutly worshiping the Son of God, their pagan counterparts were paying homage to the Sun God. During the 270s, Roman Emperor Aurelian brought the cult of Sol Invictus, or 'The Unconquered Sun,' into the spotlight, with its feast day falling on December 25. John Carroll University historian Joseph F. Kelly notes that other Romans also revered the Persian god Mithra, whose feast day may have been on December 25 as well. Additionally, there was Saturnalia, a Roman festival held annually from December 17 to December 23. By the time Christianity became widespread, many ancient Romans were already accustomed to December celebrations.

This occurred during Constantine’s reign in early 4th-century Rome. In 313, Constantine and his co-emperor Licinius issued the Edict of Milan, effectively legalizing Christianity and halting its persecution. As a devout Christian, Constantine dedicated his reign to spreading Christianity throughout the empire. The first known mention of December 25 as the official birthday of Jesus dates back to 336, just before Constantine’s death. As it appeared in a document listing other significant religious dates, it is assumed that a celebration likely took place, and thus 336 is often referred to as the first official 'Christmas.'

While it may never be fully known if Christians celebrated Christmas on December 25 before 336, it’s clear that the tradition quickly took hold (although marathons of A Christmas Story were still a long way off). By the close of the 4th century, Christian bishops were holding Christmas Mass across Rome, and pagan festivals began to fade away. Whether Christmas replacing earlier December traditions was a coincidence or a strategic move by the Church is still debated, though some argue it was intentional: Since Romans were already accustomed to festivities on December 25, the Church might have sought to tap into this existing celebratory spirit.

To sum up, the beginnings of Christmas are just as open to interpretation as the exact date of Jesus’s birth—so feel free to play “All I Want for Christmas Is You” whenever you like.