December Solstice Information
The Southern solstice on the earth occurs in December according to the Gregorian calendar. Common are December 21 and December 22. It is therefore also known as December solstice in Western culture.
In the Southern hemisphere it is the summer solstice, in the Northern hemisphere it is the winter solstice.
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Southern solstice solar year
See also: Tropical yearThe length of the southern solstice year has been relatively stable between 6000 BC and 2000 CE at 49:30 to 50:00 in excess of 365 days and 5 hours. After 2000 CE it is getting shorter. In 4000 CE the excess time will be 48:52 and in 10000 CE 46:45 [2]
Occurrences
Date and time in Universal Time of the Southern solstice [3]
- 2000-12-21 13:37
- 2001-12-21 19:21
- 2002-12-22 01:14
- 2003-12-22 07:04
- 2004-12-21 12:42
- 2005-12-21 18:35
- 2006-12-22 00:22
- 2007-12-22 06:08
- 2008-12-21 12:04
- 2009-12-21 17:47
- 2010-12-21 23:38
- 2011-12-22 05:30
- 2012-12-21 11:11
- 2013-12-21 17:11
- 2014-12-21 23:03
- 2015-12-22 04:48
- 2016-12-21 10:44
- 2017-12-21 16:28
- 2018-12-21 22:23
- 2019-12-22 04:19
- 2020-12-21 10:02
Human culture
Calendars
Gregorian calendar Iranian (Persian) calendarThe figures in the charts show the differences between the Gregorian calendar and Persian Jalāli calendar in reference to the actual yearly time of the Southern solstice. The error shifts by slightly less than 1/4 day per year; in the Gregorian calendar it is corrected by a leap year every 4th year, omitting three such corrections in every 400 years, so that the average length of a calendar year is 365 97/400 days; while in the Persian calendar every eighth leap-cycle is extended to 5 years, making the average 365 8/33 days, shorter than the Gregorian average by one day every 13200 years.
The date of the solstice is not the same as the date of the latest sunrise and both are not the same as the date of earliest sunset. Because the Earth is moving along its solar orbital path, for each solar day the Earth has to do more than one full rotation. Because the Earth's orbit is elliptical, the speed at which the Earth moves along its orbit varies. Consequently, solar days are not the same length throughout the year. "Mean time" is the way of correcting this, making each day the same length, i.e. 24 hours. The maximum correction (see Equation of Time) is plus or minus fifteen minutes to the mean but its value change quite rapidly around the solstices. If solar time were used rather than mean time, the latest sunrise and earliest sunset as well as the shortest day would all be at the solstice.
Commemorations
See also: Winter solsticeReferences
- ^ United States Naval Observatory (2010-06-10). "Earth's Seasons: Equinoxes, Solstices, Perihelion, and Aphelion, 2000-2020". http://www.usno.navy.mil/USNO/astronomical-applications/data-services/earth-seasons.
- ^ http://individual.utoronto.ca/kalendis/leap/Solar-Year-Length-Variations.pdf
- ^ http://www.usno.navy.mil/USNO/astronomical-applications/data-services/earth-seasons
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