Convert Time to usable Numbers

Hello, im trying to check time, but check to see if the time is within a range.

for example, check to see if time is between 12:50pm, and 30 minutes later (1:20pm)

also, i want to be able to calculate that difference (12:50 + :30 = 1:20)

does anyone have any ideas on how to handle this?

and also how to hande getting the time range?
ie. (currentTime >12:50 && currentTime < 1:20)

thanks, i hope this makes sense.