A winter solstice is an astronomical event that marks the shortest day and the longest night each year. A winter solstice happens when either of the earth’s poles tilts at the furthest angle away from the sun.
In the Northern Hemisphere, winter solstice happens in December. At the same time, the Southern Hemisphere experiences the summer solstice, which marks the longest day and the shortest night of the year. In the Southern Hemisphere, winter solstice happens in June, during which time the Northern Hemisphere experiences the summer solstice. After the winter solstice, the days become longer and the nights become shorter.