The September equinox (or southward equinox) is the moment when the
Sun appears to cross the
celestial equator, heading southward. Because of differences between the
calendar year and the
tropical year, the September
equinox may occur from September 21 to 24.
At the equinox, the Sun as viewed from the
equatorrises due east and
sets due west. Before the Southward equinox, the Sun rises and sets more northerly, and afterwards, it rises and sets more southerly.
The equinox may be taken to mark the end of
astronomical summer and the beginning of astronomical autumn (autumnal equinox) in the
Northern Hemisphere, while marking the end of astronomical winter and the start of astronomical spring (vernal equinox) in the
Southern Hemisphere.[7]
The solar point of the September equinox passed from Libra and into Virgo in −729 (730 BCE) and will enter
Leo in 2439.
Apparent movement of the Sun in relation to the horizon
At the equinox, the Sun rises directly in the east and sets directly in the west. However, because of
refraction it will usually appear slightly above the horizon at the moment when its "true" middle is rising or setting. For viewers at
the north or
south poles, it moves virtually horizontally on or above the horizon, not obviously rising or setting apart from the movement in "declination" (and hence altitude) of a little under a half (0.39) degree per day.
For observers in either hemisphere not at the poles, the Sun rises and sets more and more to the south during the 3 months following the September equinox. This period is the second half of a 6-month long southerly movement, beginning with the
June solstice when the Sun rises and sets at its most northern point.
In Japan
Autumnal Equinox Day (秋分の日, Shūbun no hi) is a public holiday.[9]Higan (お彼岸) is a Buddhist holiday exclusively celebrated by Japanese sects during both the Spring and Autumnal Equinox.
In Korea,
Chuseok is a major harvest festival and a three-day holiday celebrated around the Autumn Equinox.
The
Mid-Autumn Festival is celebrated on the 15th day of the 8th
lunar month, often near the autumnal equinox day, and is an official holiday in mainland China, Hong Kong,
Taiwan and in many countries with a significant Chinese minority. As the lunar calendar is not synchronous with the Gregorian calendar, this date could be anywhere from mid-September to early October.
The traditional East Asian calendars divide a year into 24
solar terms (节气, literally "climatic segments"), and the autumnal equinox (Qiūfēn,
Chinese and
Japanese: 秋分;
Korean: 추분;
Vietnamese: Thu phân) marks the middle of the autumn season. In this context, the
Chinese character 分 means "(equal) division" (within a season).
Judaism
The Jewish
Sukkot usually falls on the first
full moon after the northern hemisphere autumnal equinox, although occasionally (In the modern Jewish calendar, three times every 19 years) it will occur on the second full moon.
Dożynki is a Slavic harvest festival. In pre-Christian times the feast usually fell on the autumn equinox.
The Southward equinox was "New Year's Day" in the
French Republican Calendar, which was in use from 1793 to 1805. The
French First Republic was proclaimed and the
French monarchy was abolished on September 21, 1792, making the following day (the equinox day that year) the first day of the "Republican Era" in France. The start of every year was to be determined by astronomical calculations following the real Sun and not the mean Sun.
The traditional
harvest festival in the United Kingdom was celebrated on the Sunday of the full moon closest to the September equinox.
Neopaganism
Neopagans observe the September equinox as a cardinal point on the
Wheel of the Year. In the Northern Hemisphere some varieties of paganism adapt
Autumn Equinox traditions. In the Southern Hemisphere, the vernal equinox corresponds with
Ostara.
Americas
The reconstructed
Cahokia Woodhenge, a large
timber circle located at the
Mississippian cultureCahokiaarchaeological site near
Collinsville, Illinois,[10] is the site of annual equinox and solstice sunrise observances. An announcement for the 2017 observance said "Out of respect for Native American beliefs, no rituals or ceremonies will be held at the free event. But visitors will stand in the same place where the Mississippian people once gathered to watch the sun rise."[11][12][13]