Device downtime calculation during performance measure hours

Hello,
I am trying to find a way to calculate our devices downtime during our performance measures hours for each month. As of now i take each shift, each day for the entire month and i add up the downtime. I would like to use a formula to make that easier. Example:

Our PM hours are Monday-Friday 5am-9pm. We have 3 Shifts: 1st-6a-2p, 2nd-2p-10p and 3rd- 10p-6a.
If a devices goes out on Monday at 3am and comes back into service on Wednesday at 4 pm it would have a downtime total of 43 hours, see below.

Each shift has a set amount of hours a devices is under performance measures: 1st- 8 hours, 2nd- 7 hours and 3rd- 1 hour (if the device is down for the entire shift)

Monday: devices goes out on 3rd shift (10p-6am) at 3am, PM start at 5am so 1 hour Monday for 3rd shift. 2nd shift (6a-2p) devices is down entire shift so 8 hours (9 hours so far) 2nd shift (2p-10p) PM stop at 9 pm so 2p-9p will be 7 hour. This will repeat for Tuesday as well.
Wedensday- still 1 hour for 3rd shift, 8 hours for 1st shift but it comes back in at 4p on 2nd shift so 2-4p will be 2 hours for a total of 43 hours down.

Now here's the hard part (for me): we have a shift change log for each shift to keep track of the devices OOS, at the end of the month i go through each shift to find how long each device is out for. Is there a way to have excel keep track of each device for an entire month? or for the length of time it is OOS? If i could have it just calculate for each shift that's fine i can add them up at the end of the month, what i'm trying to avoid is having to count each hour for each shift so id like a formula that will total it all for me and i can just add the totals together.

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If you include the date along with the time, excel can keep track of the hours. Use 24 hr time format.

By the way, your cameras caught me a few years ago. Well, not really caught ... I received a bill for the toll. Neat.

How would i do that? lol, we dont catch people lol thats another company! we just monitor the interstate!

how would i do that?

This is perfect, only draw back, when i enter a time into the "in" section it gives me an invalid format. How would i be able to enter the time the device came back into service?