Solar term

The Twenty-Four Solar Terms—— knowledge in China of time and practices developed through observation of the sun’s annual motion
UNESCO Intangible Cultural Heritage
Country	China
Reference	647
Region	Asia and the Pacific
Inscription history
Inscription	2013 (11th session)
List	Representative
UNESCO Cultural Heritage

The 24 solar terms with labels in Traditional Chinese Characters

(Twenty-four) solar terms

Solar term

Term	Longitude	Dates
Lichun	315°	4–5 February
Yushui	330°	18–19 February
Jingzhe	345°	5–6 March
Chunfen	0°	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 jiéqì, traditional Chinese: 節氣; simplified Chinese: 节气) is any of twenty-four moments in traditional Chinese lunisolar calendars that matches a particular astronomical event and signifies some natural phenomenon. The points are spaced 15° apart along the ecliptic and are used by Chinese lunisolar calendar to stay synchronized with the seasons, which is crucial for agrarian societies. The solar terms are also used to calculate intercalary months; which month is repeated depends on the position of the sun at the time.

According to the Book of Documents (書經; Shūjīng), the first determined term was Dongzhi (Winter Solstice) by Dan, the Duke of Zhou (周公旦; Zhōu Gōng Dàn), 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 (). Then four terms of seasons were set, which were soon evolved as eight terms; not until the Taichu Calendar of 104 BC were all twenty-four solar terms officially included in the Chinese calendar.

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 (候; hòu), so there are 72 pentads in a year, consisting of five, rarely six, days. Most of them are 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. 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.

Numbering

The solar terms used to mark the midpoint of the month (marked with "Z", for Chinese: 中氣; pinyin: zhōngqì ) are considered the major terms, while the solar terms used to mark the start of the month (marked with "J", for Chinese: 節氣; pinyin: jiéqì ) are deemed minor. The year starts with Lichun (J1) and ends with Dahan (Z12).

Multilingual list

Season	Chinese zodiac & Earthly Branch of Month	Sun's ecliptic longitude	Chinese name	Korean name	Vietnamese name	Japanese name	Ryukyuan (Okinawan) name	English name (Hong Kong Observatory)	English name (CCTV)	Gregorian Date (± 1 day)	Reference for Month Intercalating	Corresponding Western astrological sign
Spring	Tiger () ()	315°			(立春)			Spring commences	Beginning of Spring	Feb 4	1st month initial	Aquarius
		330°			(雨水)			Rain water	Rain Water	Feb 19	1st month midpoint	Pisces
	Rabbit () ()	345°	()		(驚蟄)		; ;	Insects waken	Awakening of Insects	Mar 6	2nd month initial
		0°			(春分)			Vernal equinox	Spring Equinox	Mar 21	2nd month midpoint	Aries
	Dragon () ()	15°			(清明)			Bright and clear	Pure Brightness	Apr 5	3rd month initial
		30°	()		(穀雨)			Corn rain	Grain Rain	Apr 20	3rd month midpoint	Taurus
Summer	Snake () ()	45°			(立夏)			Summer commences	Beginning of Summer	May 6	4th month initial
		60°	()		(小滿)			Corn forms	Grain Buds	May 21	4th month midpoint	Gemini
	Horse () ()	75°	()		(芒種)			Corn on ear	Grain in Ear	Jun 6	5th month initial
		90°			(夏至)			Summer solstice	Summer Solstice	Jun 21	5th month midpoint	Cancer
	Goat () ()	105°			(小暑)			Moderate heat	Minor Heat	Jul 7	6th month initial
		120°			(大暑)			Great heat	Major Heat	Jul 23	6th month midpoint	Leo
Autumn	Monkey () ()	135°			(立秋)			Autumn commences	Beginning of Autumn	Aug 8	7th month initial
		150°	()		(處暑)			End of heat	End of Heat	Aug 23	7th month midpoint	Virgo
	Rooster () ()	165°			(白露)			White dew	White Dew	Sep 8	8th month initial
		180°			(秋分)			Autumnal equinox	Autumn Equinox	Sep 23	8th month midpoint	Libra
	Dog () ()	195°			(寒露)			Cold dew	Cold Dew	Oct 8	9th month initial
		210°			(霜降)			Frost	Frost's Descent	Oct 23	9th month midpoint	Scorpio
Winter	Pig () ()	225°			(立冬)			Winter commences	Beginning of Winter	Nov 7	10th month initial
		240°			(小雪)			Light snow	Minor Snow	Nov 22	10th month midpoint	Sagittarius
	Rat () ()	255°			(大雪)			Heavy snow	Major Snow	Dec 7	11th month initial
		270°			(冬至)			Winter solstice	Winter Solstice	Dec 22	11th month midpoint	Capricorn
	Ox () ()	285°			(小寒)			Moderate cold	Minor Cold	Jan 6	12th month initial
		300°			(大寒)			Severe cold	Major Cold	Jan 20	12th month midpoint	Aquarius

Chinese mnemonic song

The "Song of Solar Terms" (traditional Chinese: 節氣歌; simplified Chinese: 节气歌; pinyin: jiéqìgē) is used to ease the memorization of jieqi:

Traditional Chinese

Simplified Chinese

Pinyin

The first four lines provides a concise version of the names of the 24 jieqi. The last four lines provide some rules of thumb about the Gregorian dates of jieqi, namely:

• Two jieqi per month;
• Gregorian dates are off by one or two days at most;
• In the first half of the year, jieqi happens around the 6th and 21st day of each (Gregorian) month;
• In the second half of the year, jieqi happens around the 8th and 23rd day of each (Gregorian) month.

Determination

Chart with the solar terms and their Vietnamese names

The modern definition using ecliptic longitudes, introduced by the Shixian calendar, is known as dìngqì fǎ (定氣法; 'steady term method'). Under this method, the determination of solar terms is similar to the astronomical determination of the special cases of equinox and solstice dates, with different ecliptic longitudes to solve for. One can start with an approximation and then perform a correction using the anomalies and mean motion of the sun. The JPL Horizons On-Line Ephemeris System may be used to query for exact times of solar terms.

The older method, called the píngqì fǎ (平氣法; 'equal term method'), simply divides the tropical year into 24 equal parts.

See also

• Chinese calendar
• Korean calendar
• Japanese calendar
• Vietnamese calendar
• Wheel of the Year

External links

• 24 Solar Terms calculator
• 24 Solar Terms – Hong Kong Observatory
• Twenty Four Solar Terms and Their Customs in China
• Chinese calendar with upcoming solar terms in current year
• 24 Sekki – NAOJ > ECO > Glossary >
• Twenty-four Solar Terms and meaning
• Date and time of Solar Terms
• The 24 Solar Terms