Sorry, but I'm pretty sure all throughout the story I keep all the mentions of hour in the format of 24:00. I don't really see why you need to do the math to change it to AM & PM format.
I mean like- Cause I ain't used to a 24 hour system, I have to like- keep subtracting 12 and shit to figure out the time in AM and PM. An option to change the clock to a 12 hour system would be nice for people like me who ain't used to 24 hour systems.
17-2=15 and the number in the ones place is the time but it's probably confusing but easy 22 is 10 and 20 is 8. I hope my mini lesson provided a little help with 24 hour clocks.