Nine-to-five means the usual office hours: start at nine in the morning, finish at five in the afternoon. People also say “a nine-to-five job” for ordinary desk work, Monday to Friday, and “the nine-to-five” for that whole way of life — regular hours, then home. Though actually, many office workers do not start at nine or leave at five any more, and shops, hospitals, and factories never did. The phrase still stuck. Sometimes it sounds a little tired, as if the speaker wants a freer day. It is everyday English, not fancy.

朝九晚五