Solar term


A solar term is any of twenty-four periods 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.
According to the Book of Documents, the first determined term was the Winter Solstice, also named Dongzhi by Zhou Gong, while he was trying to locate the geological center of his kingdom, by measuring the length of the sun's shadow on an ancient timekeeper instrument named Tu Gui . Then four terms of seasons were set, which were soon evolved as eight terms; until 104 B. C. in the book Taichu Calendar, the entire twenty-four solar terms were 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. Each solar term is divided into three , so there are 72 pentads in a year. Each pentad consists of five, rarely six, days, and are mostly named after phenological 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.
On December 1, 2016, the Solar Terms were listed as UNESCO's Intangible Cultural Heritage.

List of solar terms

Sun's ecliptic
longitude		Chinese
name		Korean nameVietnamese
name		Japanese
name		Ryukyuan
name		Gregorian
Date
Reference for
Month Intercalating		RemarkCorresponding Astrological Sign
315°立春
lìchūn		立春
ipchun/ripchun		Lập xuân 立春（りっしゅん）
risshun		立春（りっしゅん）
risshun		Feb 41st month initialSpring Begins
Aquarius
330°雨水
yǔshuǐ		雨水
usu		Vũ thủy 雨水（うすい）
usui		雨水（うしー）
ushii		Feb 191st month midpointMore Rain Than Snow
Pisces
345°驚蟄
jīngzhé		驚蟄
gyeongchip		Kinh trập 啓蟄（けいちつ）
keichitsu		驚く（うどぅるく）
uduruku
驚くー（おどるくー）
udurukuu
虫驚（むしうどぅるく）
mushi'uduruku		Mar 62nd month initialHibernating Insects Awaken
Pisces
0°春分
chūnfēn		春分
chunbun		Xuân phân 春分（しゅんぶん）
shunbun		春分（すんぶん）
sunbun		Mar 212nd month midpointSpring Center
Aries
15°清明
qīngmíng		淸明
cheongmyeong		Thanh minh 清明（せいめい）
seimei		清明（しーみー）
shiimii		Apr 53rd month initialClear and Bright
Aries
30°穀雨
gǔyǔ		穀雨
gogu		Cốc vũ 穀雨（こくう）
kokuu		穀雨（くくー）
kukuu		Apr 203rd month midpointWheat Rain
Taurus
45°立夏
lìxià		立夏
ipha/ripha		Lập hạ 立夏（りっか）
rikka		立夏（りっかー）
rikkaa		May 64th month initialSummer Begins
Taurus
60°小滿
xiǎomǎn		小滿
soman		Tiểu mãn 小満（しょうまん）
shōman		小満（すーまん）
suuman		May 214th month midpointCreatures Plenish
Gemini
75°芒種
mángzhòng		芒種
mangjong		Mang chủng 芒種（ぼうしゅ）
bōshu		芒種（ぼーすー）
boosuu		Jun 65th month initialSeeding Millet
Gemini
90°夏至
xiàzhì		夏至
haji		Hạ chí 夏至（げし）
geshi		夏至（かーちー）
kaachii		Jun 215th month midpointSummer Maximum Cancer
105°小暑
xiǎoshǔ		小暑
soseo		Tiểu thử 小暑（しょうしょ）
shōsho		小暑（くーあちさ）
kuu'achisa		Jul 76th month initialA bit Sweltering
Cancer
120°大暑
dàshǔ		大暑
daeseo		Đại thử 大暑（たいしょ）
taisho		大暑（うーあちさ）
uu'achisa		Jul 236th month midpointMost Sweltering
Leo
135°立秋
lìqiū		立秋
ipchu/ripchu		Lập thu 立秋（りっしゅう）
risshū		立秋（りっすー）
rissuu		Aug 87th month initialAutumn Begins
Leo
150°處暑
chǔshǔ		處暑
cheoseo		Xử thử 処暑（しょしょ）
shosho		処暑（とぅくるあちさ）
tukuru'achisa		Aug 237th month midpointHeat Withdraws
Virgo
165°白露
báilù		白露
baekno/baekro		Bạch lộ 白露（はくろ）
hakuro		白露（ふぁくるー）
fakuruu		Sep 88th month initialDews
Virgo
180°秋分
qiūfēn		秋分
chubun		Thu phân 秋分（しゅうぶん）
shūbun		秋分（すーぶん）
suubun		Sep 238th month midpointAutumn Center
Libra
195°寒露
hánlù		寒露
hanlo		Hàn lộ 寒露（かんろ）
kanro		寒露（かんるー）
kanruu		Oct 89th month initialCold Dews
Libra
210°霜降
shuāngjiàng		霜降
sanggang		Sương giáng 霜降（そうこう）
sōkō		霜降（しむくだり）
shimukudari		Oct 239th month midpointFrostScorpio
225°立冬
lìdōng		立冬
ipdong/ripdong		Lập đông 立冬（りっとう）
rittō		立冬（りっとぅー）
rittuu		Nov 710th month initialWinter Begins
Scorpio
240°小雪
xiǎoxuě		小雪
soseol		Tiểu tuyết 小雪（しょうせつ）
shōsetsu		小雪（くーゆち）
kuuyuchi		Nov 2210th month midpointSnows a bit
Sagittarius
255°大雪
dàxuě		大雪
daeseol		Đại tuyết 大雪（たいせつ）
taisetsu		大雪（うーゆち）
uuyuchi		Dec 711th month initialSnows a lot
Sagittarius
270°冬至
dōngzhì		冬至
dongji		Đông chí 冬至（とうじ）
tōji		冬至　（とぅんじー）
tunjii		Dec 2211th month midpointWinter Maximum
Capricorn
285°小寒
xiǎohán		小寒
sohan		Tiểu hàn 小寒（しょうかん）
shōkan		小寒（すーかん）
suukan		Jan 612th month initialA bit Frigid
Capricorn
300°大寒
dàhán		大寒
daehan		Đại hàn 大寒（だいかん）
daikan		大寒（でーかん）
deekan		Jan 2012th month midpointMost Frigid
Aquarius

The "Song of Solar Terms" is used to ease the memorization of jiéqì:

;Traditional Chinese:
春雨驚春清穀天
夏滿芒夏暑相連
秋處露秋寒霜降
冬雪雪冬小大寒
每月兩節不變更
最多相差一兩天
上半年來六、廿一
下半年是八、廿三
;Simplified Chinese:
春雨惊春清谷天
夏满芒夏暑相连
秋处露秋寒霜降
冬雪雪冬小大寒
每月两节不变更
最多相差一两天
上半年来六、廿一
下半年是八、廿三
;Pinyin
chūn yǔ jīng chūn qīng gǔ tiān,
xià mǎn máng xià shǔ xiāng lián,
qiū chù lù qiū hán shuāng jiàng,
dōng xuě xuě dōng xiǎo dà hán.
měi yuè liǎng jié bù biàn gēng,
zùi duō xiāng chā yī liǎng tiān
shàng bàn nián lái liù, niàn yī
xià bàn nián shì bā, niàn sān

Regional note

In Japan, the term Setsubun originally referred to the eves of Risshun Rikka, Risshū, and Rittō, 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.