The winter solstice is the shortest day of the year, when your part of Earth tilts farthest away from the sun. In the Northern Hemisphere (which includes the United States, Europe, and most of Asia), this happens around December 21. On this day, the sun rises late, sets early, and reaches its lowest point in the sky at noon. If you live far north, you might get only six or seven hours of daylight, while places near the Arctic Circle stay dark almost all day.

Ancient people tracked the winter solstice carefully because after it passes, the days finally start getting longer again: the sun begins its slow climb back toward summer.

Many cultures celebrate the winter solstice as a turning point, a promise that winter's darkness won't last forever. The ancient Romans held the festival of Saturnalia around this time. Stonehenge in England was built thousands of years ago to mark the solstices with sunrise alignments. Today, some people still gather to watch the sunrise on the solstice, celebrating the moment when light begins winning back the day.

The Southern Hemisphere has its winter solstice around June 21, when the north enjoys its longest day.