Yup that was my take too. Just a trick of the language I guess. I mean, when I wake up at 2:37am I don't think "What am I doing up in the beginning of the morning?" I think "Middle of the night."

I'm with you Puccini.
Also, even if that weren't the case "tonight" doesn't feel that off.
But really I think you're right. Both of them had been awake all night and for all we know the might be like 4 or 5 in the morning which still makes it "tonight" in my book.

I don't think it needed fixing This conversation took place at the end of a long and stressfull "shift".
If you're working long hours, it doesn't really matter what the time is, your day ends when you go to sleep. At least that's my experience.

I think there was a miss in the dialogue as Bishop says "F#ck your rules Nathan" and then Muir says something to the effect of "Okay, but tonight my rules kept you alive". I think he should have said "last nite my rules kept you alive".
That is what I could not figure out. Not sure why they did not fix that.

This seemed to be the following morning as Muir was still in his tuxedo from the prior evening. I think there was a miss in the dialogue as Bishop says "F#ck your rules Nathan" and then Muir says something to the effect of "Okay, but tonight my rules kept you alive". I think he should have said "last nite my rules kept you alive".
I almost numchucked you, you don't even realize!