|(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.
Solar terms originated in China, then spread to Korea, Vietnam, and Japan, countries in the East Asian cultural sphere. This is exhibited by the fact that traditional Chinese, Hanja, and Kanji characters for most of the solar terms are identical.
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.
List of solar terms
|285°||First Term of Cold Season||小寒
|Tiểu hàn||Jan 6|
|300°||Second Term of Cold Season||大寒
|Đại hàn||Jan 20|
|Lập xuân||Feb 4|
|330°||First Term of Rainy Season||雨水
|Vũ thủy||Feb 19||more rain than snow|
|345°||Last Term of Cold Season||驚蟄 (惊蛰)
|Kinh trập||Mar 6||lit. awakening of hibernating insects. See the note at Chinese calendar#Solar term.|
|Xuân phân||Mar 21||lit. spring division (or center)|
|15°||Last Term of Rainy Season||清明
|Thanh minh||Apr 5||time for tending graves|
|30°||Second Term of Rainy Season||穀雨 (谷雨)
|Cốc vũ||Apr 20||lit. grain rain: rain helps grain grow|
|Lập hạ||May 6|
|60°||First Term of Growing Season||小滿 (小满)
|Tiểu mãn||May 21||grains are plump|
|75°||Second Term of Growing Season||芒種 (芒种)
|Mang chủng||Jun 6||lit. awns (beard of grain) grow|
|Hạ chí||Jun 21||lit. summer extreme (of sun's height)|
|105°||First Term of Hot Season||小暑
|Tiểu thử||Jul 7|
|120°||Second Term of Hot Season||大暑
|Đại thử||Jul 23|
|Lập thu||Aug 8|
|150°||Last Term of Hot Season||處暑 (处暑)
|Xử thử||Aug 23||lit. dwell in heat|
|165°||First Term of Dew Season||白露
|Bạch lộ||Sep 8||condensed moisture makes dew white|
|Thu phân||Sep 23||lit. autumn division (or center)|
|195°||Second Term of Dew Season||寒露
|Hàn lộ||Oct 8|
|210°||Last Term of Dew Season||霜降
|Sương giáng||Oct 23||appearance of frost and descent of temperature|
|Lập đông||Nov 7|
|240°||First Term of Snowy Season||小雪
|Tiểu tuyết||Nov 22|
|255°||Second Term of Snowy Season||大雪
|Đại tuyết||Dec 7|
|Đông chí||Dec 22||lit. winter extreme (of sun's height)|
- the Yushi and Jingzhe have been exchanged by Liu Xin in Han dynasty, the original solar term is the Last Term of Cold Season
- the Jingzhe and Yushi have been exchanged by Liu Xin in Han dynasty, and the original solar term is the First Term of Rainy Season
- the Qingmin and Guyu have been exchanged by Liu Xin in Han dynasty, and the original solar term is the Second Term of Rainy Season.
- the Guyu and Qingmin have been exchanged by Liu Xin in Han dynasty, and the original solar term is the Last Term of Rainy Season.
- 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.