How to count hours

As always, the more set in their ways a person is, the harder it is to write code which will be compatible with their system.

This will work if and ONLY if you type in times in the exact format which are given in the examples. And, as SHG stated, this one will also only work on hours in the same day.

That,
and it's 24 lines of code.
Been a little slow in the office here today :P

I left the steps which I took at the bottom, so you can go over the progression of the nightmare of gobbledeegook which is the final result.

Lemme know what you think, I'm still kinda new to this, so I'm mashing what I know with examples I find in order to make stuff work the way I want it to.