you go clubbing for 18 hours? they arent even open that long lol. you KNOW what 12 hour stretch you are currently in.if you were trapped in that cave for a week, the time would be the least of your concerns.
you mean subjectively?by looking out a window...if you honestly ever don't simply know whether it's AM or PM, you need to get your sleep schedule in order
Well if you live in northern places in the world like Scandinavia, Canada or even northern Russia, you would know that in the winters, the sky lights up at 8 AM and goes dark 4 PM.