Bar O'Clock: time for the pub!
A term used primarily in universities to indicate a customary time to meet for drinks. So, if a group always meets at 6pm on Friday to unwind, they will refer to that time as 'Bar O'Clock'.
The term can imply not only an actual time, but a place - for example "are you coming to Bar O'Clock?" asks if you are following the usual routine of both same time, same place as you usually have your wacky adventures.
I have also encountered this in the Australian Defence Force, and several workplaces. Of course, it's more prevalent amongst the lucky students who can afford to participate in a Bar O'Clock tradition!