The shortest day of the year is the winter solstice, which occurs in December in the northern hemisphere and in June in the southern hemisphere. It marks the first day of winter. Either the North Pole or the South Pole reach their maximum tilt away from the Sun at the winter solstice. At the December solstice, the Sun is directly over the Tropic of Capricorn. For the June solstice, the Sun is directly over the Tropic of Cancer.
- The winter solstice marks the shortest day of the year. But, the date depends on which side of the equator you live on.
- The shortest day of the year is December 21 or 22 in the northern hemisphere.
- The shortest day of the year is June 20 or 21 in the southern hemisphere.
- When it’s the shortest day of the year in the northern hemisphere, it’s the longest day of the year in the southern hemisphere (and vice versa).
When Is the Shortest Day of the Year?
The solstice is an instantaneous even all over the world, so what day it is when it happens depends on where you live. For example, the December solstice of 2022 occurs on Wednesday, December 21 in the western hemisphere, but it will already be Thursday, December 22 in the eastern hemisphere. But, it’s only the shortest day of the year if you live in the northern hemisphere. The shortest day of the year in the southern hemisphere was the solstice at 5:13 EDT on June 21.
How Long Is the Shortest Day of the Year?
The length of the day depends on where you live. At the pole tilted away from the Sun, there actually is no day because the Sun doesn’t rise above the horizon. Meanwhile, the Sun doesn’t set at the opposite pole. Near the equator, the solstice does not make a difference and the day is 12 hours long. The effect of the solstice increases as you move toward the poles.
The length of the shortest and longest days varies over time because the axis of the Earth’s rotation is not a constant. It oscillates between 22.1 and 24.5 degrees over the course of 41,000 years. Right now, the angle is 23.44° and decreasing. So, the shortest day of the year is getting slightly longer each year. Many, many years in the future, the angle starts increasing and the shortest day starts getting longer again.
- Astronomical Applications Department of USNO. “Earth’s Seasons – Equinoxes, Solstices, Perihelion, and Aphelion.”
- Meeus, Jean (2009). Astronomical Algorithms (2nd English ed.). Richmond, Virginia: Willmann-Bell, Inc. ISBN 978-0-943396-61-3.
- U.S. Naval Observatory Nautical Almanac Office (1992). P. Kenneth Seidelmann (ed.). Explanatory Supplement to the Astronomical Almanac. University Science Books. ISBN 978-0-935702-68-2.