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°.
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]
