21:57 is 9:57...
1-12... obviously same as digital.
13- 1
14- 2
15- 3
16- 4
17- 5
18- 6
19- 7
20-8
21-9
22-10
23- 11
24- that would be midnight... and the minutes don't change.
For exampe, pretend it's 19:21, the hour changes but not the minutes. That would be 7:21...