when; at what moment
Almost always used in the fixed expression いつ何時 (いつなんどき), meaning 'at any time' or 'whenever'. The standalone use is rare.
See also: いつ何時 (いつなんどき)
You never know when a disaster might strike.
what time
Dated term for 'what time'. Modern Japanese uses 何時 (なんじ) instead. This reading may appear in older texts.
See also: 何時 (なんじ)
I am ready at any time.
People in the past asked 'What time is it?' using なんどき.
at any time; at any moment · when; at what moment
Standard kanji spelling, but note that 何時 is also read なんじ (what time) and いつ (when). Context usually disambiguates.
Combination of 何 (なん, 'what') and 時 (どき, 'time'). The reading どき is a voiced variant of とき used in compounds.