什么时候
shén me shí hou · HSK 2
when
⏰ 什么 (what) + 时候 (time/moment) = what time = when
什么 means 'what' and 时候 means 'time' or 'moment', so literally 'what moment'. 时 is the time/hour character (sun radical 日 + measure), and 候 means a period or season.
时 — sun 日 + temple/measure 寺
Originally a phono-semantic compound: 日 (sun) gives the meaning of time or season, while 寺 (shí) supplies the sound. Early forms used 之 as the phonetic before 寺 replaced it. The core sense 'season, time, hour' has stayed stable since ancient Chinese.