Solar term

[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.

Solar terms originated in China, then spread to Korea, Vietnam, and Japan, countries in the East Asian cultural sphere.

[8] 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 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: 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 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 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 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: The modern definition using ecliptic longitudes, introduced by the Shixian calendar, is known as 定气法 (dìng qì fǎ, 'steady term method').