# Solar term

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 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. 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; 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). 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 [zh] (候; 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. 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 (Beijing 2022 Winter Olympics) | Gregorian Date (± 1 day) | Reference for Month Intercalating | Corresponding Western astrological sign |
| Spring | Tiger (虎) ‹See RfD› Yín (寅) | 315° | 立春 ‹See RfD› lìchūn | 立春 (입춘/립춘) ‹See RfD› ipchun/ripchun | Lập xuân (立春) | 立春（りっしゅん） ‹See RfD› risshun | 立春（りっしゅん） ‹See RfD› risshun | Spring commences | Beginning of Spring | Feb 4 | 1st month initial | Aquarius |
| Spring | Tiger (虎) ‹See RfD› Yín (寅) | 330° | 雨水 ‹See RfD› yǔshuǐ | 雨水 (우수) ‹See RfD› usu | Vũ thủy (雨水) | 雨水（うすい） ‹See RfD› usui | 雨水（うしー） ‹See RfD› ushii | Rain water | Rain Water | Feb 19 | 1st month midpoint | Pisces |
| Spring | Rabbit (兔) ‹See RfD› Mǎo (卯) | 345° | 驚蟄 (惊蛰) ‹See RfD› jīngzhé | 驚蟄 (경칩) ‹See RfD› gyeongchip | Kinh trập (驚蟄) | 啓蟄（けいちつ） ‹See RfD› keichitsu | 驚く（うどぅるく） ‹See RfD› uduruku; 驚くー（おどるくー） ‹See RfD› udurukuu; 虫驚（むしうどぅるく） ‹See RfD› mushi'uduruku | Insects waken | Awakening of Insects | Mar 6 | 2nd month initial | Pisces |
| Spring | Rabbit (兔) ‹See RfD› Mǎo (卯) | 0° | 春分 ‹See RfD› chūnfēn | 春分 (춘분) ‹See RfD› chunbun | Xuân phân (春分) | 春分（しゅんぶん） ‹See RfD› shunbun | 春分（すんぶん） ‹See RfD› sunbun | Vernal equinox | Spring Equinox | Mar 21 | 2nd month midpoint | Aries |
| Spring | Dragon (龍) ‹See RfD› Chén (辰) | 15° | 清明 ‹See RfD› qīngmíng | 淸明 (청명) ‹See RfD› cheongmyeong | Thanh minh (清明) | 清明（せいめい） ‹See RfD› seimei | 清明（しーみー） ‹See RfD› shiimii | Bright and clear | Pure Brightness | Apr 5 | 3rd month initial | Aries |
| Spring | Dragon (龍) ‹See RfD› Chén (辰) | 30° | 穀雨 (谷雨) ‹See RfD› gǔyǔ | 穀雨 (곡우) ‹See RfD› gogu | Cốc vũ (穀雨) | 穀雨（こくう） ‹See RfD› kokuu | 穀雨（くくー） ‹See RfD› kukuu | Corn rain | Grain Rain | Apr 20 | 3rd month midpoint | Taurus |
| Summer | Snake (蛇) ‹See RfD› Sì (巳) | 45° | 立夏 ‹See RfD› lìxià | 立夏 (입하/립하) ‹See RfD› ipha/ripha | Lập hạ (立夏) | 立夏（りっか） ‹See RfD› rikka | 立夏（りっかー） ‹See RfD› rikkaa | Summer commences | Beginning of Summer | May 6 | 4th month initial | Taurus |
| Summer | Snake (蛇) ‹See RfD› Sì (巳) | 60° | 小滿 (小满) ‹See RfD› xiǎomǎn | 小滿 (소만) ‹See RfD› soman | Tiểu mãn (小滿) | 小満（しょうまん） ‹See RfD› shōman | 小満（すーまん） ‹See RfD› suuman | Corn forms | Grain Buds | May 21 | 4th month midpoint | Gemini |
| Summer | Horse (馬) ‹See RfD› Wǔ (午) | 75° | 芒種 (芒种) ‹See RfD› mángzhòng | 芒種 (망종) ‹See RfD› mangjong | Mang chủng (芒種) | 芒種（ぼうしゅ） ‹See RfD› bōshu | 芒種（ぼーすー） ‹See RfD› boosuu | Corn on ear | Grain in Ear | Jun 6 | 5th month initial | Gemini |
| Summer | Horse (馬) ‹See RfD› Wǔ (午) | 90° | 夏至 ‹See RfD› xiàzhì | 夏至 (하지) ‹See RfD› haji | Hạ chí (夏至) | 夏至（げし） ‹See RfD› geshi | 夏至（かーちー） ‹See RfD› kaachii | Summer solstice | Summer Solstice | Jun 21 | 5th month midpoint | Cancer |
| Summer | Goat (羊) ‹See RfD› Wèi (未) | 105° | 小暑 ‹See RfD› xiǎoshǔ | 小暑 (소서) ‹See RfD› soseo | Tiểu thử (小暑) | 小暑（しょうしょ） ‹See RfD› shōsho | 小暑（くーあちさ） ‹See RfD› kuu'achisa | Moderate heat | Minor Heat | Jul 7 | 6th month initial | Cancer |
| Summer | Goat (羊) ‹See RfD› Wèi (未) | 120° | 大暑 ‹See RfD› dàshǔ | 大暑 (대서) ‹See RfD› daeseo | Đại thử (大暑) | 大暑（たいしょ） ‹See RfD› taisho | 大暑（うーあちさ） ‹See RfD› uu'achisa | Great heat | Major heat | Jul 23 | 6th month midpoint | Leo |
| Autumn | Monkey (猴) ‹See RfD› Shēn (申) | 135° | 立秋 ‹See RfD› lìqiū | 立秋 (입추/립추) ‹See RfD› ipchu/ripchu | Lập thu (立秋) | 立秋（りっしゅう） ‹See RfD› risshū | 立秋（りっすー） ‹See RfD› rissuu | Autumn commences | Beginning of Autumn | Aug 8 | 7th month initial | Leo |
| Autumn | Monkey (猴) ‹See RfD› Shēn (申) | 150° | 處暑 (处暑) ‹See RfD› chǔshǔ | 處暑 (처서) ‹See RfD› cheoseo | Xử thử (處暑) | 処暑（しょしょ） ‹See RfD› shosho | 処暑（とぅくるあちさ） ‹See RfD› tukuru'achisa | End of heat | End of Heat | Aug 23 | 7th month midpoint | Virgo |
| Autumn | Rooster (雞) ‹See RfD› Yǒu (酉) | 165° | 白露 ‹See RfD› báilù | 白露 (백로) ‹See RfD› baengno | Bạch lộ (白露) | 白露（はくろ） ‹See RfD› hakuro | 白露（ふぁくるー） ‹See RfD› fakuruu | White dew | White Dew | Sep 8 | 8th month initial | Virgo |
| Autumn | Rooster (雞) ‹See RfD› Yǒu (酉) | 180° | 秋分 ‹See RfD› qiūfēn | 秋分 (추분) ‹See RfD› chubun | Thu phân (秋分) | 秋分（しゅうぶん） ‹See RfD› shūbun | 秋分（すーぶん） ‹See RfD› suubun | Autumnal equinox | Autumn Equinox | Sep 23 | 8th month midpoint | Libra |
| Autumn | Dog (狗) ‹See RfD› Xū (戌) | 195° | 寒露 ‹See RfD› hánlù | 寒露 (한로) ‹See RfD› hallo | Hàn lộ (寒露) | 寒露（かんろ） ‹See RfD› kanro | 寒露（かんるー） ‹See RfD› kanruu | Cold dew | Cold Dew | Oct 8 | 9th month initial | Libra |
| Autumn | Dog (狗) ‹See RfD› Xū (戌) | 210° | 霜降 ‹See RfD› shuāngjiàng | 霜降 (상강) ‹See RfD› sanggang | Sương giáng (霜降) | 霜降（そうこう） ‹See RfD› sōkō | 霜降（しむくだり） ‹See RfD› shimukudari | Frost | Frost's Descent | Oct 23 | 9th month midpoint | Scorpio |
| Winter | Pig (豬) ‹See RfD› Hài (亥) | 225° | 立冬 ‹See RfD› lìdōng | 立冬 (입동/립동) ‹See RfD› ipdong/ripdong | Lập đông (立冬) | 立冬（りっとう） ‹See RfD› rittō | 立冬（りっとぅー） ‹See RfD› rittuu | Winter commences | Beginning of Winter | Nov 7 | 10th month initial | Scorpio |
| Winter | Pig (豬) ‹See RfD› Hài (亥) | 240° | 小雪 ‹See RfD› xiǎoxuě | 小雪 (소설) ‹See RfD› soseol | Tiểu tuyết (小雪) | 小雪（しょうせつ） ‹See RfD› shōsetsu | 小雪（くーゆち） ‹See RfD› kuuyuchi | Light snow | Minor Snow | Nov 22 | 10th month midpoint | Sagittarius |
| Winter | Rat (鼠) ‹See RfD› Zǐ (子) | 255° | 大雪 ‹See RfD› dàxuě | 大雪 (대설) ‹See RfD› daeseol | Đại tuyết (大雪) | 大雪（たいせつ） ‹See RfD› taisetsu | 大雪（うーゆち） ‹See RfD› uuyuchi | Heavy snow | Major Snow | Dec 7 | 11th month initial | Sagittarius |
| Winter | Rat (鼠) ‹See RfD› Zǐ (子) | 270° | 冬至 ‹See RfD› dōngzhì | 冬至 (동지) ‹See RfD› dongji | Đông chí (冬至) | 冬至（とうじ） ‹See RfD› tōji | 冬至（とぅんじー） ‹See RfD› tunjii | Winter solstice | Winter Solstice | Dec 22 | 11th month midpoint | Capricorn |
| Winter | Ox (牛) ‹See RfD› Chǒu (丑) | 285° | 小寒 ‹See RfD› xiǎohán | 小寒 (소한) ‹See RfD› sohan | Tiểu hàn (小寒) | 小寒（しょうかん） ‹See RfD› shōkan | 小寒（すーかん） ‹See RfD› suukan | Moderate cold | Minor Cold | Jan 6 | 12th month initial | Capricorn |
| Winter | Ox (牛) ‹See RfD› Chǒu (丑) | 300° | 大寒 ‹See RfD› dàhán | 大寒 (대한) ‹See RfD› daehan | Đại hàn (大寒) | 大寒（だいかん） ‹See RfD› daikan | 大寒（でーかん） ‹See RfD› deekan | Severe cold | Major Cold | Jan 20 | 12th month midpoint | Aquarius |

## Chinese mnemonic song

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

The modern definition using ecliptic longitudes, introduced by the Shixian calendar, is known as 定气法 (‹See RfD› dìng qì fǎ, '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 is known as 平气法 (‹See RfD› píng qì fǎ, 'equal term method') and simply divides the tropical year into 24 equal parts.

## Regional note

In Japan, the term ‹See RfD› Setsubun (節分) originally referred to the eves of ‹See RfD› Risshun (立春, 315°, the beginning of Spring), ‹See RfD› Rikka (立夏, 45°, the beginning of Summer), ‹See RfD› Risshū (立秋, 135°, the beginning of Autumn), and ‹See RfD› Rittō (立冬, 225°, the beginning of Winter), but currently mostly refers to the day before ‹See RfD› 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.