Why is Christmas on December 25?

Everyone knows that on December 25 unto us a child was born. He was born of historic lineage and became so popular that his legacy was mediated by fiction. Of course, I am referring to Humphrey Bogart. Yes, my friend, Bogart was born Dec. 25, 1899. Interestingly, Warner Bros circulated the rumor that he was born on January 23, 1900, hoping to avoid the Christ-typology.

What is my point, you ask? To you, I offer the simple lesson: don't bogart that point, my friend. Sometimes people weren't born when we think they were.

In the first six centuries of Christian expansion, Christianity was practiced somewhat differently from city to city (and importantly, from East to West). The date established for Jesus’ birth is an example of this variety. By the end of the 2nd century, May 20, March 21, and multiple dates in April were suggested for Jesus’ birthdate (I specify these dates using the modern calendar for clarity). Some eastern cities celebrated Jesus’ birth on what we now consider to be January 6. Concurrently, many other cities celebrated Jesus’ birth on what we now consider December 25. But it wasn’t until the 6th century that December 25 became the standard date for most cities that worshipped according to the Christian calendar.

While the subject of Jesus’ birth was interesting to Christians as early as the first century, our earliest sources—e.g. Paul’s letters and Mark’s Gospel—do not include nativity stories. And while Paul mentions a commemorative festival related to Jesus’ death (1 Cor 5:7-8), there is no evidence that the nativity stories of Matthew and Luke were celebrated as annual feasts until centuries later. And because neither Matthew nor Luke suggest a date for Jesus’ birth, later theologians were left to suggest, guess, and surmise when Jesus might have been born. December 25 was probably not seriously considered until the fourth century. (For more detailed names, places, and dates, see Thomas J. Talley, Origins of the Liturgical Year).

While Jesus’ birthdate was unknown to his first-century followers and disputed among later theologians, one assumption was common: every writer on this topic believed that Jesus’ birth was a theological event. In other words, God got involved and so the date probably wasn’t random. Whatever date it was, it would have to be theologically significant. Using this premise it became commonplace to believe that Jesus was crucified on the same date that that he was divinely conceived. Surmising that Jesus was crucified on March 25 (John’s Gospel associates Jesus’ crucifixion with the Jewish Passover feast; 14 Nisan), some theologians guessed that Jesus was also conceived on March 25. Andrew McGowan explains,

Connecting Jesus’ conception and death in this way will certainly seem odd to modern readers, but it reflects ancient and medieval understandings of the whole of salvation being bound up together.

Indeed, according to this logic, there are no coincidences in the divine plan. "In all the gin joints in all the towns in all the world . . . " 

Because many Christians believed that Jesus was conceived on March 25, they looked to December 25 as a logical birthdate, as it is nine months after conception. Others believed that Jesus was both crucified and conceived on April 6. Thus January 6 (being nine months later than Apr. 6) made better sense. In keeping with the logic that great theological events happen on important theological dates, many Christians also believed that Jesus baptism also happened on January 6. Indeed Christians in the Armenian Church continue to celebrate Christmas on January 6 (I envy their ability to wait until after the New Year for gift shopping).

The difference between December 25 and January 6 might help explain two things: (1) it explains why some churches eventually held feasts on both dates; (2) it also explains the tradition that there are 12 days of Christmas (thus measuring the time elapsed between Dec. 25 and Jan. 6).

Modern minds will no doubt have difficulty with the logic used to determine these dates. In order for one to conclude that Jesus was born on December 25 (for example), one must make four assumptions. First, we must grant that God chooses significant dates to intervene in human history. Second, we must grant that Jesus’ conception and death took place on the same date. Third, we must grant that March 25 is in fact the date that Jesus was crucified (which is disputed among historians) and so too was the date he was conceived. Fourth, we must grant that Jesus’ gestation period was exactly nine calendar months.

From the modern historian’s perspective, we must conclude that we haven’t the first clue of Jesus’ birthdate. Rather, December 25 is a theological guess that was not widely commemorated until the 6th century.  What I find most interesting, however, is that commemorating the life of Jesus restructured how Christians thought about their annual calendar. Conversely, once a commemorative calendar had been established, these traditions eventually restructured how Christians thought about Jesus.

This is just one of the fundamental things about history that apply
As time goes by