It is quarter past 12.
00:15 \ 12:15
It is 4 o'clock.
4:00 \ 16:00
It is quarter past 1.
1:15 \ 13:15
It is half past 7.
7:30 \ 19:30
It is quarter to 10.
9:45 \ 21:45
It is one o'clock.
1:00 \ 13:00
It is half past 2.
2:30 \ 14:30
It is quarter past 4.
4:15 \ 16:15
It is half past 11.
11:30 \ 23:30
It is half past 12.
00:30 \ 12:30