One of the most interesting aspects of living out at sea is that you completely lose your sense of time. You measure things in terms of cruises instead of weeks, and in ports of call instead of days. Yesterday was Bar Harbor, today is Saint John, tomorrow is Halifax. I can tell you that it is Wednesday, but only because I just pulled out my phone to check.
This occurs across all cruises and itineraries. You can be sailing in 7-day circles around Mexico, landing in Los Angeles every Saturday, and you still never know what day it is. The longer the cruise and more varied the itinerary, the less likely it is that anybody has a clue.
I suppose that we never know what day it is because we never need to know. We don't have weekends to look forward to; we aren't counting down to anything. Saturday and Sunday are workdays just like any other. You finish your work at night and you go to the bar to hang out with your friends and have a few drinks, and then your alarm clock goes off far too early and you swear you're going to bed at a decent hour tonight, and then you go to the bar anyway. It's a vicious cycle of Friday nights and Monday morning that never ends.
If this sounds exhausting - it's because it is. I remember once hearing one of the kids who worked in the Officers' Mess excitedly talking about tomorrow being their "day off". In cruise ship speak, here's what that meant: she had to to be there from 5:30am to 9:00am to serve breakfast, and then again from 6:00pm to 11:00pm to serve dinner - an 8 1/2 hour day - but she didn't have to be there from 11:00 - 2:00 for lunch. That's a day off. Three hours less in your work day.
Why do we party so hard and stay up so late, then, if our work days can be so hard? Because if you don't, you go insane. You need that relaxation, that camaraderie - to feel like a normal human being. If you all you ever do is finish your workday and go to bed - you don't make any friends. You don't have a life. So you party like it's Friday, and you get up in the morning.