As the Northern Hemisphere tilts 23.5 degrees away from the sun on December 21, winter will officially be here.

While the occasion might not sound like cause for celebration, the winter solstice is the source of many festive traditions.

Solstice means “standing still sun” in Latin since the sun seems to remain in the same spot throughout the day. It’s believed the tradition of celebrating the solstice started with the fear that the fading light of the sun wouldn’t return unless people kept watch and celebrated throughout the night.

One tradition observed in Northern Europe during the winter solstice was to burn a Yule log all night. What was reason for the nightlong fire? To cleanse the air of the previous year’s events. The log’s ashes were then collected and saved, because people believed they had medicinal uses and could guard against evil.

While we use the winter solstice to mark the beginning of winter, during pre-medieval times Celtic Brits and Gaelic Europeans regarded the solstice as the end of the winter season. Their reasoning? Following the shortest day of the year, the days actually start becoming longer. They would have a feast to celebrate, which often included a Yule log cake.

As the Northern Hemisphere tilts 23.5 degrees away from the sun on December 21, winter will officially be here

In ancient Rome, the winter solstice was observed with a festival called Saturnalia. Servants would dine with their masters and a mock king would be elected to oversee the festivities. To mark the occasion, schools would close and people would parade through the streets.

While Stonehenge was built for the summer solstice, Newgrange in Ireland was made for the winter solstice. At 10 a.m. when the sun is brightest, rays of light shine through its dome’s small passageway – the only time when engravings on the wall called the Triple Spiral become illuminated without artificial light. Fun fact: Newgrange is older than both Stonehenge and the Egyptian pyramids, built around 3200 B.C. during the neolithic period.

The winter solstice may be the darkest day of the year, but it’s not usually the coldest. Since oceans are slow to warm and cool, they still maintain some of the warmth of summer in December. The coldest days of winter usually follow a month and a half later.

It’s believed that the December 25 date of Christmas was derived from the winter solstice. Eastern churches traditionally celebrated Christmas on January 6 (what’s known as the Epiphany). As Christmas celebrations moved west, early church leaders attempted to attract pagans to Christianity by adding Christian meaning to the winter solstice celebrations. These December celebrations eventually became the new date for Christmas.