The traditional East Asian calendars divide a year into 24 solar terms (節氣). Gǔyù (pīnyīn) or more commonly pronounced as Gǔyǔ, or Kokuu (rōmaji) (Traditional Chinese: 穀雨; Simplified Chinese: 谷雨; Japanese: 穀雨; Korean: 곡우; Vietnamese: Cốc vũ; literally: "grain rain") is the 6^th solar term. It begins when the Sun reaches the celestial longitude of 30° and ends when it reaches the longitude of 45°. It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 30°. In the Gregorian calendar, it usually begins around April 20 and ends around May 5.

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 Guyu include:

China

• First pentad: 萍始生
• Second pentad: 鳴鳩拂其羽
• Last pentad: 戴勝降于桑

Japan

• First pentad: 葭始生
• Second pentad: 霜止出苗
• Last pentad: 牡丹華