not know the time of day

not know the time of day

To be completely unintelligent, daft, or not alert. We paid for her to attend the best university in the state, but three years in, she still doesn't know the time of day. How can you expect me to respect my boss when he doesn't even know the time of day?
See also: know, not, of, time
Farlex Dictionary of Idioms.

know the time of day

be well informed about something.
See also: know, of, time
Farlex Partner Idioms Dictionary
See also:
  • know the time of day
  • slow study
  • (as) daft as a brush
  • daft as a brush
  • daft
  • I wasn't born yesterday
  • poophead
  • not the full quid
  • make (one) feel small
References in periodicals archive
Amateur historian Dr Naylor Firth, of Itton, Monmouthshire, told the BBC: "We do not know the time of day he died.
Death of Able Seaman Richard Morgan, 26