Wikipedia
Chunfen
The traditional East Asian calendars divide a year into 24 solar terms (節氣). Chūnfēn ( pīnyīn), Shunbun ( rōmaji), or Chunbun/Ch'unbun ( romaja) 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°. 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 20 March and ends around 4 April (5 April East Asia time).