In terms of SI units, it is 61800 seconds.
15 hours, 50 minutes, 46.15 seconds
It is then 1045
17.1667 hrs
11:15
1.5678 x 1030 approximately.
If you want it in English, it would be, "The English class is at 1030 tomorrow morning."
9:45
13 hours and 15 minutes.
6 hours 30 minutes
12 hours and 30 minutes.
6 hours and 30 minutes.