December Solstice: Shortest day of the year in the Northern Hemisphere
The December solstice is on either December 20, 21, 22 or 23. It is called Winter Solstice in the Northern Hemisphere, where it is the shortest day of the year. In the Southern Hemisphere, it is the Summer Solstice and the longest day of the year.See also: Ten things you might not know about December Solstice
The Sun's position
The Sun is directly overhead of the Tropic of Capricorn in the Southern Hemisphere during the December Solstice.
The December Solstice occurs when the Sun reaches its most southerly declination of -23.5 degrees. In other words, when the North Pole is tilted furthest – 23.5 degrees – away from the Sun.
When is the December solstice?
December Solstice in New York, New York, U.S.A. is on
Monday, December 21, 2015 at 11:48 PM EST (Change city)
December Solstice in Universal Coordinated Time is on
Tuesday, December 22, 2015 at 04:48 UTC
Midnight Sun or complete darkness
Being the longest day of the year, also means that people in the areas south of the Antarctic Circle towards the South Pole will see the Midnight Sun, i.e. have 24 hours of daylight, during this time of the year.
For people in the Northern Hemisphere, the December solstice marks the exact opposite, the day of the year with fewest hours of daylight. North of the Arctic Circle towards the North Pole there is no daylight at all during this time of the year.
Solstices importance in culture
The December solstice has played an important role in cultures worldwide from ancient times until our day. Even Christmas celebrations are closely linked to the observance of the December solstice.
The December solstice in the calendar
December 21 or 22 solstices happen more often than December 20 and 23 solstices. The last December 23 solstice was in 1903 and will not happen again until 2303. A December 20 solstice has occurred very rarely, with the next one in the year 2080.(*)
Why do the dates vary?
As with the June solstice, the December solstice’s varying dates are mainly due to the calendar system. The Gregorian calendar, which is used in most western countries, has 365 days in a common year and 366 days in a leap year.
However, the tropical year, which is the length of time the sun takes to return to the same position in the seasons cycle (as seen from Earth), is different to the calendar year. The tropical year is approximately 365.242199 days but varies from year to year because of the influence of other planets. The exact orbital and daily rotational motion of the Earth, such as the “wobble” in the Earth's axis (precession), also contributes to the changing solstice dates.
The solstices can also be observed by noting the point of time when the sun rises or sets as far south as it does during the course of the year (winter in the northern hemisphere) or maximally north (summer in the northern hemisphere).
December solstice and seasons
It is important to note that Earth does not move at a constant speed in its elliptical orbit. Therefore the seasons are not of equal length: the times taken for the sun to move from the vernal equinox to the summer solstice, to the autumnal equinox, to the winter solstice, and back to the vernal equinox are roughly 92.8, 93.6, 89.8 and 89.0 days respectively. The consolation in the northern hemisphere is that spring and summer last longer than autumn and winter (when the December solstice occurs).
The relative position of the Earth's axis to the sun changes during the cycle of seasons. This phenomenon is the reason why the sun’s height above the horizon changes throughout the year. It is also responsible for the seasons through controlling the intensity and duration of sunlight received at various locations around the planet.
End of the world in Mayan calendar
(*) All dates refer to Coordinated Universal Time (UTC). Dates may vary depending on the time zone.
In this Article
- The Sun's position
- When is the December solstice?
- Darkness in the north
- Solstices in culture
- December 20, 21, 22 or 23
- Why do the dates vary?
- Solstices & seasons
- End of the world predictions
Equinox & Solstice
Watch daylight move across the planet... More