It’s 23 to 9 (Alternative clock system).

20:37

It’s 23 to 9.

Correct answer

20:36

It’s 24 to 9.

Error: 1 minute earlier

19:51

It’s 9 to 8.

Error: read minutes starting from hour markings and adding minutes

19:40

It’s 20 to 8.

Error: confuse hour and minute hands