As our ancestors huddled around their fires on dark and cold winter nights, some of them noticed patterns in the sky that repeated as the seasons changed. One of the patterns noticed was days grew shorter and nights longer as winter progressed and then reversed. Over time they measured this phenomenon and created observatories to mark when this moment of reverse happened. They held feasts and celebrations to mark the day the sun would return to melt the snow, grow their crops, and warm them.
The winter solstice event has be documented as early as 432 BC in ancient Greece and in China from about the 4th century BC. Celebrations or festivals around the winter solstice include Saturnalia (Rome, from 479 BC), Yule (ancient Germanic tribes), Yalda Night (502 BC, Iran), and Dongzhi Festival (China, about 500 BC).
The knowledge the winter solstice is probably even older than the written record shows. Newgrange is a huge tomb located in County Meath in northeastern Ireland with a history of more than 5,000 years, which is even older than Stonehenge. Only the first sunshine of the Winter Solstice can shine into the inner chamber of the tomb. The most popular way to celebrate Winter Solstice here is the annual lottery draw, and the only 60 lucky fellows can enter the Newgrange tomb at sunrise to welcome the only sunshine of the year.
It was not until 354 AD that a Festival of the Nativity was documented which eventually became Christmas. So Christmas is a relative recent holiday this time of year.
So no matter what your beliefs or traditions, the winter solstice is an indication of the coming of spring and that is a reason to celebrate!