The winter solstice, which marks the shortest day and longest night of the year in the Northern Hemisphere, is set to occur on December 21. After that, the days will slowly start getting longer again.
The date and time of the solstice changes slightly each year, but the 2023 winter solstice is set for December 21 at 10:27 p.m. Eastern time. However, it can sometimes occur on December 22, and on rare occasions has been observed as early as December 20 or as late as December 23. The exact time of the solstice is based on Coordinated Universal Time (UTC), which is five hours ahead of Eastern time.
The winter solstice marks the beginning of astronomical winter in the Northern Hemisphere. During the solstice, the sun rises and sets at its southernmost points on the horizon, and the sun appears directly over the Tropic of Capricorn, the southernmost point at which the sun can be seen straight overhead (90 degrees above the horizon). The low sun angle means people will cast their longest midday shadow of the year on the winter solstice, assuming skies are clear.
The word “solstice” comes from the Latin word “solstitium,” which means “sun standing still.” This is because the sun appears to pause in its daily southward movement in the sky on the December solstice. Afterward, the position of sunrise and sunset shifts northward again and daylight slowly begins to increase.
The solstice occurs because Earth’s axis is tilted from the vertical by about 23.5 degrees, causing each hemisphere to receive different amounts of sunlight throughout the year. This means that while December 21 marks the first day of astronomical winter in the Northern Hemisphere, the precise start of winter can vary based on different definitions – astronomical winter runs until the spring equinox in March, meteorological winter runs from December 1 to February end, and solar winter starts in early November and lasts until early February.
After the solstice, daylight starts to increase, with cities at higher latitudes closer to the North Pole experiencing more rapid gains in sunlight. In history, people have celebrated the solstices with rituals such as bonfires and ceremonial dances to mark the passage of seasons. The cold, dark days of the solstice have played a significant role in various cultures and traditions, and many prehistoric monuments and landmarks around the world were built to mark the sun’s changing path in the sky. Stonehenge, perhaps the most famous of these, was once a solar calendar used to track the seasons.