Condition Formulas for Counting hours between Time Shifts

Hi guys!

I need a non-macro formula to help solve the following scenarios. Ideally this formula would be all encompassing (to include other scenarios as well if something similar were to come up in the future):

Scenario 1:
Start Time End Time
A 12:00:00 AM 12:00:00 AM
B 6:00:00 PM 6:00:00 AM

Scenario 2:
Start Time End Time
A 12:00:00 AM 6:00:00 AM
B 6:00:00 PM 6:00:00 AM

Scenario 3:
Start Time End Time
A 6:00:00 PM 2:00:00 AM
B 6:00:00 PM 6:00:00 AM

Scenario 4:
Start Time End Time
A 8:00:00 AM 5:00:00 PM
B 6:00:00 PM 6:00:00 AM

If A occurs between B (or vice versa), then calculate how many hours from A occur between B. So it should calculate the following:

Scenario 1: 12 hours
Scenario 2: 6 hours
Scenario 3: 8 hours
Scenario 4: 0 hours (Because A does not occur between B)

This can be broken down into several simpler formulas which would show the steps to get to the final answer.

Thanks so much for your help!

This is assuming that everything occurs on the same day, in a single-day time span.

A is considered a shift
B is considered a rule of which the shift must abide to. Therefore, A must be applied to B in the time-span of a single day (technically, B can also be seen as 12:00:00 AM-6:00:00 AM AND 6:00:00 PM-12:00:00 AM).

For Scenario 1:
Row A represents 24 hours.
To apply it to Row B:
12:00:00 AM - 6:00:00 AM would be 6 hours
6:00:00 PM - 12:00:00 AM would be 6 hours
Add them up to equal 12 hours total to apply to the rule of 6:00:00 PM - 6:00:00 AM.

Keep asking questions as this is a complicated situation.