From 6:15pm to 7:15am is 13 hours.
2 hours.
21 hours
There are 16 hours from 4 am to 8 pm. 4 am to 4 pm is 12 hours, then 4 pm to 8 pm is another 4 hours.
It is seven hours from 9 AM to 4 PM.
10 hours and 45 minutes.
7:45 am to 6:15 pm is 10 hours 15 minutes (101/4 hours)
From 8am to 6:15pm is 10 hours and 15 minutes.
There are 10.25+24k where k is an integer.
6:15am to 5pm is 10 hours and 45 minutes.
8.5 + 24k hours where k is any integer.
From 6:15am to 1:30pm is 7 hours and 15 minutes.
There are 9 and 1/2 hours between 8:45 am and 6:15 pm.
13 + 24k hours where k is an integer.
From 6:15pm to 7:15am is 13 hours.
From 2:37 am to 6:15 am is 3 hours and 38 minutes. From 2:37 am to 6:15 pm is 15 hours and 38 minutes. From 2:37 pm to 6:15 pm is 3 hours and 38 minutes. From 2:37 pm to 6:15 am is 15 hours and 38 minutes.
12 Hours ! There are 12 hours in the AM and 12 hours in the PM !