Why is Christmas on December 25?

Sol Invictus

The choice of December 25 for Christmas is deeply intertwined with the Roman festival of Sol Invictus. Gary Arndt explains that while the winter solstice originally fell on December 25, by the time of Emperor Aurelian, it had shifted to December 21. Despite this, the Romans maintained their traditional calendar dates, and when Christianity spread, it often absorbed pagan customs to ease conversion 1. The festival of Sol Invictus, celebrating the unconquered sun, was established in 275 AD and coincided with this date 2.

Christmas falls on the day of the Roman pagan festival of Sol Invictus, which was on December 25, which at one time was the winter solstice.

--- Gary Arndt

This alignment with Sol Invictus was not arbitrary, as it facilitated the integration of Christian traditions into existing Roman celebrations 1.

   

March 25

March 25 holds significant importance in early Christianity, influencing the selection of December 25 as Christmas. Gary Arndt notes that early Christians believed Jesus was conceived on March 25, aligning with the spring equinox and the creation of the world 1. This belief stemmed from the idea that prophets died on the same day they were conceived, and Jesus was thought to have died on March 25.

March 25 was also believed to be the day that the world was created.

--- Gary Arndt

By setting Jesus' conception on March 25, his birth was naturally placed nine months later, on December 25, thus intertwining with the Roman festival of Sol Invictus 1.