A solstice occurs twice a year when the sun reaches its highest or lowest point in the sky at noon, resulting in the longest and shortest days of the year. The two solstices are the summer solstice, around June 21, when the Northern Hemisphere experiences the longest day, and the winter solstice, around December 21, when it has the shortest day. During the summer solstice, the sun is directly over the Tropic of Cancer, while during the winter solstice, it is over the Tropic of Capricorn. These events mark the changing of seasons and have been celebrated in various cultures throughout history.