Chunfen

The traditional East Asian calendars divide a year into 24 solar terms . Chūnfēn or Shunbun is the 4^th solar term. It begins when the Sun reaches the celestial longitude of 0° and ends when it reaches the longitude of 15°. It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 0°. In the Gregorian calendar, it usually begins around March 20 and ends around April 4 .

Pentads

Each solar term can be divided into 3 pentads . They are: first pentad , second pentad and last pentad . Pentads in Chunfen include:

; China
* First pentad: 玄鳥至
* Second pentad: 雷乃發聲
* Last pentad: 始雷

; Japan
* First pentad: 雀始巣
* Second pentad: 桜始開
* Last pentad: 雷乃発声