Midnight is 12:00 am
12:00 am = 0 hours past midnight
No add 1 for each hour after:
1:00 am is 1 hour after
2:00 am is 2 hours after
3:00 am is 3 hours after
4:00 am is 4 hours after
5:00 am is 5 hours after
6:00 am is 6 hours after
7:00 am is 7 hours after
8:00 am is 8 hours after
9:00 am is 9 hours after
10:00 am is 10 hours after
11:00 am is 11 hours after
12:00 pm is 12 hours after
1:00 pm is 13 hours after
2:00 pm is 14 hours after
3:00 pm is 15 hours after
4:00 pm is 16 hours after
5:00 pm is 17 hours after
6:00 pm is 18 hours after
7:00 pm is 19 hours after
8:00 pm is 20 hours after
9:00 pm is 21 hours after
10:00 pm is 22 hours after
11:00 pm is 23 hours after
12:00 am = 0 hours past midnight