like night and day

like night and day

Completely different; totally or nearly opposite. Her transformation has really been like night and day. She doesn't even look like the same person since she started the program. A: "Have you seen any improvement in his behavior?" B: "Oh, it's like night and day. He's been a model student this month."
See also: and, like, night
Farlex Dictionary of Idioms.

like night and day

If two things are like night and day, they are completely different. `Compare him with last year and it's like night and day,' his teammate said. Note: People also sometimes just say that two things are night and day. The two stories are night and day.
See also: and, like, night
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • (you) coulda fooled me
  • (you) could have fooled me
  • metamorphose into
  • a bright spark
  • the other way around
  • the other way around/round
  • the other way round
  • other way round
  • bother about
  • bother about (someone or something)