The traditional East Asian calendars divide a year into 24 solar terms. Yǔshuǐ, Usui, Usu, or Vũ thủy is the 2nd solar term. It begins when the Sun reaches the celestial longitude of 330° and ends when it reaches the longitude of 345°. It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 330°. In Gregorian calendar, it usually begins around 18 February (19 February East Asia time) and ends around 5 March.
Pentads
Each solar term can be divided into three pentads (候). They are first pentad (初候), second pentad (次候) and last pentad (末候). Pentads in Yushui including:
China
First pentad: 獺祭魚, 'Otters make offerings of fish'. As fish begin to swim upstream, they are hunted by otters, which are believed to offer the fish to heaven.
Second pentad: 鴻雁來, 'The wild geese arrive'. Wild geese begin to make their northward migration, following the onset of spring.
Last pentad: 草木萌動, 'Trees and grass put forth shoots'.
