Does this exist? App that adds up sleep hours

I'd like to make it a bit easier to track my pup's sleep. Currently I'm just using the stopwatch on my phone to sort of time how long she sleeps and how long she's awake. Then I have do math. Sleepdeprived math. I'd love it if there was an app or something out there where , for example, I can click a button when she's asleep and again when she's awake and then the app nicely adds it all up and tells me her total sleeping and waking hours. Something like that.

I'm very tired and I don't want to do more math.