Autumnal equinox
Publiée le 2007-09-21
Autumnal equinox
In the northern hemisphere, the autumnal equinox corresponds to the moment when the apparent longitude of the Sun is equal to 180 degrees. Our calendar (the Gregorian calendar) is built to preserve a fixed date for the beginning of the seasons. The date of the autumnal equinox is in 2007 on September 23 at 9:50 UT (on September 23 at 11h: 50 French standard time). Since the creation of the Gregorian calendar (1582) the autumnal equinox falls on the 21st, 22nd, 23rd or 24th of September. Generally it falls on the 22nd or 23rd of September. It will fall on September 21st in 2092 and it will be the first time since the creation of the Gregorian calendar. That will reproduce in 2096, and then it will be necessary to wait the year 2464 so that it falls on September 21st again. It fell one September 24th in 1803, 1807, 1903, 1907, 1911, 1915, 1919, 1923, 1927 and 1931, and will fall again on this date in 2303 and that will be the last time. The day of the equinox, if we disregard atmospheric refraction, the duration of the night is equal to the duration of the day. It is also the day when the Sun rises due east and sets due south. The autumnal equinox in the Northern hemisphere corresponds to the spring equinox in the Southern hemisphere.
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