Chunfen Explained

See also: March equinox. The traditional Chinese calendar divides a year into 24 solar terms.^[1] Chūnfēn, Shunbun, Chunbun, or Xuân phân is the 4th solar term. It begins when the Sun reaches the celestial longitude of 0° and ends when it reaches the longitude of 15°. In the Gregorian calendar, it usually begins around 20 March and ends around 4 April (5 April East Asia time). It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 0°.

Pentads

Each solar term can be divided into 3 pentads (候). They are: first pentad (初候), second pentad (次候) and last pentad (末候). Pentads in Chunfen include:

China

First pentad: 玄鳥至, 'The dark birds arrive'. 'Dark bird' in this case refers to swallows, which are also making their northward migration.^[2]
Second pentad: 雷乃發聲, 'Thunder sounds', referring to the onset of spring thunderstorms.^[2]
Last pentad: 始電, 'Lightning begins'. This refers to thunderstorms as well, but also to the gradual lengthening of daytime, and the prevalence of sunlight.^[2]

Japan

See also: Vernal Equinox Day. A pentad as follows was referred to Japanese traditional calendar presented in a smaller, easy to use, format.

First pentad:, 'Sparrow begins holding a nest'.^[3]
Second pentad:, 'Cherry blossoms open for the first time'.^[3]
Last pentad:, 'Distant thunder start to sound'.^[3]

Notes and References

Zhang . Peiyu . Hunag . Hongfeng(. The Twenty-four Solar Terms of the Chinese Calendar and the Calculation for Them . Purple Mountain Observatory . 1994 . 9 March 2021 . 12 June 2021 . https://web.archive.org/web/20210612151759/https://en.cnki.com.cn/Article_en/CJFDTotal-GXKK403.013.htm . dead .
Book: 新加纂録類 (Shinka Sanrokurui) . 改定史籍集覧 (Kaitei Shiseki Shūran) . 19 . Kondō Heijō (近藤瓶城) . 110 . 近藤活版所 (Kondō Kappansho) . Tokyo . 1901 . (Meiji 34) .
Book: Fujisawa, Morihiko. 図説日本民俗学全集 (Zusetsu Nihon Minzokugaku Zenshū) . 年中行事編 (Nenjū Gyōjihen) . 7 . 103 . Akane Shobō . 1961 . Tokyo .