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Seasons Applet Press "y" key to increase or "Y" to decrease the year. Open the Java Console of your browser to get details. Seasons from 2000 to 3000 The algorithm computing the seasons used in my Java applet was taken from the book of Meeus. It is valid for the years 1000 to 3000, and for several centuries after 3000 with errors still quite small. The accuracy is about 1 minute nowadays.   USNO (U.S. Naval Observatory) UT Seasons Applet UT 2003 Spring Equinox 2003 Summer Solstice 2003 Autum Equinox 2003 Winter Solstice Mar 21 01:00 June 21 19:10 Sept 23 10:47 Dec 22 07:04 01:00 19:11 10:47 07:04 2004 Spring Equinox 2004 Summer Solstice 2004 Autum Equinox 2004 Winter Solstice Mar 20 06:49 June 21 00:57 Sept 22 16:30 Dec 21 12:42 06:49 00:57 16:30 12:42 2005 Spring Equinox 2005 Summer Solstice 2005 Autum Equinox 2005 Winter Solstice Mar 20 12:33 June 21 06:46 Sept 22 22:23 Dec 21 18:35 12:34 06:46 22:23 18:35 2013 Spring Equinox 2013 Summer Solstice 2013 Autum Equinox 2013 Winter Solstice Mar 20 11:02 June 21 05:04 Sept 22 20:44 Dec 21 17:11 11:02 05:04 20:44 17:11 Data for the perihelon and aphelion by MICA (Multiyear Interactive Computer Almanac 1990-2005, USNO): Apparent Geocentric Positions (True Equinox and Ecliptic of Date): MICA Seasons Applet Perihelion 2004, Jan 04 17:33 UT until 17:51 UT R=0.983264836 AU 17:47 UT R=0.983265 AU Aphelion 2004, Jul 05 10:45 UT until 11:02 UT R=1.016693679 AU 10:07 UT R=1.016694 AU Spring equinox: is the beginning of spring (vernal equinox). Nowadays, it occurs on March 19, 20 or 21 in the Northern Hemisphere. year UT date 1796 March 19 1797 to 2007 March 20 or 21 2008 to 2043 March 20 2044 March 19 2045 to 2101 March 19 or 20 Summer solstice: is the beginning of summer. It occurs on June 20 or 21 in the Northern Hemisphere. Autumnal equinox: is the beginning of autumn. It occurs on September 21, 22 or 23 in the Northern Hemisphere. year UT date 1582 to 2091 September 22 or 23 2092 September 21 Winter solstice: is the beginning of winter. It occurs on on December 20, 21 or 22 in the Northern Hemisphere.

Dates of Solstices and Equinoxes 2000 to 2100:

Dates of Spring Equinoxes 1780 to 2120:

 

The Gregorian Calendar Reform (1582): The Gregorian calendar year is intended to be of the same length as the cycle of the seasons. The mean time between two successive vernal equinoxes is called a tropical year, and it is about 365.2422 days long. To synchronize the calendar and tropical years, leap days are periodically added to the calendar. Leap Years: According to the Gregorian calendar years evenly divisible by 4 are leap years (a 29th day in February), with the exception of centurial years that are not evenly divisible by 400. Therefore, the years 1700, 1800, 1900 and 2100 are not leap years, but 1600, 2000, and 2400 are leap years. Gregorian calendar: 1 year = (365 + 1/4 - 1/100 + 1/400 = 365.2425) days = 365.2425 days The difference is 0.0003 days or 26 seconds per year. It will take about 3300 years before the Gregorian calendar is as much as one day out of step with the seasons.   Open the Java Console (Java Messages window) of your browser to get details:     Please visit my pages: GeoAstro Applet Collection Astronomy by JavaScript Web Links How does the Sun appear to move across our sky? Earth's Seasons, Equinoxes, Solstices, Perihelion, and Aphelion 2000-2020 (USNO) Seasons of the Year Jahreszeiten The Equinoxes and Solstices (Royal Observatory Greenwich) The seasons (Royal Observatory Greenwich) Leap Years (USNO) The Gregorian Calendar Reform (Papal Bull "Inter Gravissamas") Tropical Year Why March 21st? The Seasons and the Earth's Orbit - Milankovitch Cycles (USNO) This Restless Globe The Lengths of the Seasons (on Earth) The Northern Hemisphere Seasons, by Numerical Integration Date and Time of Vernal Equinox (NASA/GISS) Last Modified: 2023 Oct.  03