History of Christmas: Why do we celebrate it on December 25?


Here begins our series of articles on the History of Christmas. Advent begins this Sunday.


Advent means the “coming” of the Christ Child. The Advent Season is marked by the four Sundays before Christmas and is celebrated in the church calendar as one the most festive seasons of the year. This year is a bit unusual: as Christmas is on a Monday, the four Sundays before begin on December 3.

As we shall see in this series many of the traditions, customs, and stories of the Advent Season have Christian roots while others have non-Christian sources. Some are legendary, and others are firmly rooted in history.


It is perhaps ironic that the actual date of the Nativity or birth of the Christ Child, which our Western calendar system is based upon, is not known with certainty. Indeed, the Feast of Christmas was not an early festival for the church, like Resurrection Sunday (Easter) was, and in fact, did not see general observance until the 4th century. The western church did not agree upon the current date of December 25 until the early part of the 5th century under Pope Leo I, though this date for Christmas was first mentioned in the 4th century illuminated manuscript the Chronography of 354.


Some historians, especially in the eastern church, suggested that the date of Christmas was derived as 9 months after the Annunciation (to Mary) which is celebrated on March 25. This would place the birth of Christ on December 25. Many 18th century scholars, including Isaac Newton, argued that this date was picked to supplant the pagan year-end holiday Saturnalia that was celebrated by the Romans and many of whose customs survive today: decorations of evergreen, holly, mistletoe, feasting, and the exchange of gifts.


December 25, the ancient date for their Winter Solstice, was celebrated as the “birth of the unconquerable sun” or Dies Natalis Solis Invicti when the sun’s transit was at the lowest point on the horizon with the shortest “day” of the year and then with longer days coming began its transit northward. Under the Christian calendar the 25th was to become known as the birth of the unconquerable Son.

Bill Petro, your friendly neighborhood historian

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About billpetro

Bill Petro writes articles on history, technology, pop culture, and travel. He has been a technology sales enablement executive with extensive experience in Cloud Computing, Automation, Data Center, Information Storage, Big Data/Analytics, Mobile, and Social technologies.


  1. Jean A. on December 1, 2016 at 6:15 pm

    It’s interesting that so many modern day Christmas traditions have pagan roots, but one- the poinsetta- is a Christmas plant with actual Christan roots (albeit the story behind it is most likely a myth): “The Poinsettia’s association with Christmas began in 16th century Mexico, where legend has it that a little girl was too poor to purchase a gift for a celebration of Jesus’ birthday, so she gathered wild plants and weeds growing along side the road and placed them at her church altar; through a Christmas miracle, crimson blooms emerged from the weeds and became beautiful Poinsettias. In the 17th century, Franciscan friars in Mexico regularly included them in their Christmas decorations, with the star-shaped petals representing the Star of Bethlehem and the bright red color representing the blood of Jesus’ sacrifice on the cross.” (Source: http://www.goodsweetearth.com/blog/happy-holly-days)

    • Bill Petro on December 1, 2016 at 7:02 pm


      I don’t know that the Poinsettia is unique as a Christian tradition, but the story you reference is close to the one I recount in my article on the History of the Poinsettia.


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