There's something about the twinkling lights, decorated Christmas tree, warm hot chocolate, stuffed stockings, and family time that makes Christmas one of the world's most celebrated holidays. There's nothing like getting prepped for the big day, especially because we know it lands on the same day every single year. But why does the Christian holiday land on December 25th? Let's take a closer look.
There are two relevant running theories as to why Christmas was selected to be on December 25th every year. The first is referred to as the "history of religion" hypothesis, which says that the holiday replaced one or more pagan holidays. The second theory, known as the "computation" or "calculation" hypothesis, indicated that early Christians calculated Jesus' birthday to be December 25. According to Philipp Nothaft from the University of Oxford All Souls College, who has previously published research on the date of Christmas claims, "the two hypotheses are not mutually exclusive."
According to ancient records, a feast dedicated to the sun god, Sol Invictus, was held in the Roman Empire on December 25, which pointed to the likelihood that Christmas replaced it. There was another pagan festival named Saturnalia around the same time that lasted a few days, which could also explain why the holiday is now on the 25th. However, Christians may have celebrated Jesus' birthday on the 25th before Sol Invictus was even acknowledged, suggesting a problem with this theory. According to Nothaft, there have been many questions about how December 25 became the "occasion of a Roman feast associated with [Sol Invictus]." In fact, there is just "too little about this feast to make confident pronouncements," according to Nothaft.
The other running theory, the computation hypothesis, is the suggestion that Jesus' birthday was actually December 25th. Early Christians calculated this date by adding nine months to the day they thought of as God's conception. Some thought that the day of Jesus' crucifixion happened on March 25th, and they tagged on nine months to get December 25th, meaning early Christians say the date of Jesus' crucifixion to be the date of conception. However, it is not fully understood why early Christians chose March 25th as both the date of Jesus' crucifixion and birth, but both theories seem to be accepted by researchers.