Solar term

The 24 solar terms
(Twenty-four) solar terms
Traditional Chinese(二十四)節氣
Simplified Chinese(二十四)节气
Transcriptions
Standard Mandarin
Hanyu Pinyin(èrshísì) jiéqì
Wade–Giles(erh-shih-hsi) chieh-chi
IPA[tɕjě.tɕʰî]
Yue: Cantonese
Jyutping(ji6 sap6 sei3) zit3 hei3
Southern Min
Hokkien POJ(jī-si̍p-sù) cheh-khùi
Solar term
Term Longitude Dates
Lichun 315° 4–5 February
Yushui 330° 18–19 February
Jingzhe 345° 5–6 March
Chunfen 20–21 March
Qingming 15° 4–5 April
Guyu 30° 20–21 April
Lixia 45° 5–6 May
Xiaoman 60° 21–22 May
Mangzhong 75° 5–6 June
Xiazhi 90° 21–22 June
Xiaoshu 105° 7–8 July
Dashu 120° 22–23 July
Liqiu 135° 7–8 August
Chushu 150° 23–24 August
Bailu 165° 7–8 September
Qiufen 180° 23–24 September
Hanlu 195° 8–9 October
Shuangjiang 210° 23–24 October
Lidong 225° 7–8 November
Xiaoxue 240° 22–23 November
Daxue 255° 7–8 December
Dongzhi 270° 21–22 December
Xiaohan 285° 5–6 January
Dahan 300° 20–21 January

A solar term (or jieqi, simplified Chinese: 节气; traditional Chinese: 節氣) is any of twenty-four periods in traditional Chinese lunisolar calendars that matches a particular astronomical event or signifies some natural phenomenon.[1] The points are spaced 15° apart along the ecliptic[2] 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;[3] which month is repeated depends on the position of the sun at the time.

According to the Book of Documents, the first determined term was Dongzhi (Winter Solstice) by Dan, the Duke of Zhou, while he was trying to locate the geological center of the Western Zhou dynasty, by measuring the length of the sun's shadow on an ancient type of sundial called tǔguī [ja] (土圭).[4] Then four terms of seasons were set, which were soon evolved as eight terms; until 104 BC in the book Taichu Calendar, the entire twenty-four solar terms were officially included in the Chinese calendar.[5]

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, but it is always between 15 and 16 days. Each solar term is divided into three pentads [zh] (; hòu), 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 the North China Plain, peoples living in the different climates still use it without changes.[6] This is exhibited by the fact that traditional Chinese characters for most of the solar terms are identical.

On December 1, 2016, the solar terms were listed by UNESCO as an Intangible Cultural Heritage.[7]

  1. ^ "24 Chinese Feasts (Jiéqì, 节气), equivalent to the 24 Chinese Solar Terms". Chinese calendar. asia-home.com.
  2. ^ 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.
  3. ^ 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 歲中閏月法 lit. "midpoint intercalating system".
  4. ^ Book of Documents.
  5. ^ Ban, Gu. Book of Han.
  6. ^ 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) Maritime Japan, for example, comparing the climate of Taiyuan with that of Tokyo and Kyoto: on Japanese islands differences in seasonal gap lengths are the main problem. In subtropical or tropical regions including southern China climate difference is more serious.
  7. ^ "UNESCO – The Twenty-Four Solar Terms, knowledge in China of time and practices developed through observation of the sun's annual motion". ich.unesco.org. Retrieved 9 March 2021.