|(Twenty-four) solar terms|
|Vietnamese||(hai mươi bốn) tiết khí|
A solar term is any of 24 points in traditional East Asian lunisolar calendars that matches a particular astronomical event or signifies some natural phenomenon. The points are spaced 15° apart along the ecliptic and are used by lunisolar calendars to stay synchronized with the seasons, which is crucial for agrarian societies. The solar terms are also used to calculate intercalary months in East Asian calendars; which month is repeated depends on the position of the sun at the time.
Because the Sun's speed along the ecliptic varies depending on the Earth-Sun distance, the number of days that it takes the Sun to travel between each pair of solar terms varies slightly throughout the year. Each solar term is divided into three pentads (候 hou), so there are 72 pentads in a year. Each pentad consists of five, rarely six, days, and are mostly named after phenological (biological or botanical) phenomena corresponding to the pentad.
Solar terms originated in China, then spread to Korea, Vietnam, and Japan, countries in the East Asian cultural sphere. Although each term was named based on the seasonal changes of climate in North China Plain, peoples living in the different climates still use it with no changes. This is exhibited by the fact that traditional Chinese, Hanja, and Kanji characters for most of the solar terms are identical.
List of solar terms
|Dec 22||11th month midpoint||winter maximum (solstice)|
|Jan 6||12th month initial||a bit frigid|
|Jan 20||12th month midpoint||most frigid|
|Feb 4||1st month initial||spring begins|
|Feb 19||1st month midpoint||more rain than snow|
|Mar 6||2nd month initial||hibernating insects awaken|
|Mar 21||2nd month midpoint||spring center (equinox)|
|Apr 5||3rd month initial||clear and bright|
|Apr 20||3rd month midpoint||wheat rain|
|May 6||4th month initial||summer begins|
|May 21||4th month midpoint||creatures plentish|
|Jun 6||5th month initial||seeding millet|
|Jun 21||5th month midpoint||summer maximum (solstice)|
|Jul 7||6th month initial||a bit sweltering|
|Jul 23||6th month midpoint||most sweltering|
|Aug 8||7th month initial||autumn begins|
|Aug 23||7th month midpoint||heat withdraws|
|Sep 8||8th month initial||dews|
|Sep 23||8th month midpoint||autumn center (equinox)|
|Oct 8||9th month initial||cold dews|
|Oct 23||9th month midpoint||frost|
|Nov 7||10th month initial||winter begins|
|Nov 22||10th month midpoint||snows a bit|
|Dec 7||11th month initial||snows a lot|
- Simplified Chinese characters are shown in parentheses if they differ from the Traditional Chinese characters.
- Hanja is indicated in parentheses.
- Date can vary within a ±1 day range.
chūn yǔ jīng chūn qīng gǔ tiān,
In Japan, the term Setsubun (節分) originally referred to the eves of Risshun (立春, 315°, the beginning of Spring) Rikka (立夏, 45°, the beginning of Summer), Risshū (立秋, 135°, the beginning of Autumn), and Rittō (立冬, 225°, the beginning of Winter), but currently mostly refers to the day before Risshun. The name of each solar term also refers to the period of time between that day and the next solar term, or 1/24th of a year.
- Until 1644(Chinese Empire and its tributary states) or 1844(Japan) a period of time of the solar year itself had been equally divided instead of the spatial zodiac.
- When a lunar month's end does not reach a midpoint of the solar terms, it is regarded as the last month's intercalary one instead of the true "next" month. It is called 歳中閏月法 lit."midpoint intercalating system".
- なぜずれる？ 二十四節気と季節感 (Why off-point? -solar terms and our real feeling of the seasons) An example in Japan. It compares the climate of Taiyuan with that of Tokyo and Kyoto. In maritime Japanese islands difference of the seasonal gap length is the main problem. In subtropical or tropical regions including southern china climate difference is more serious.
- literal meaning based on the climate of North China
- the Yushi and Jingzhe have been exchanged by Liu Xin in Han dynasty.
- the Jingzhe and Yushi have been exchanged by Liu Xin in Han dynasty.
- the Qingmin and Guyu have been exchanged by Liu Xin in Han dynasty.
- the Guyu and Qingmin have been exchanged by Liu Xin in Han dynasty.