Isn't the weekend technically Sunday at 11:00 p.m. ?

These days, I'll take whatever days off I can get. Luckily, we always get Sunday off, that's my weekend. 

Not if a week ends on Saturday and starts on Sunday. 

Interesting discussion.  Four definitions I found:

the end of a week, esp. the period of time between Friday evening and Monday morning

this period as extended by one or more holidays, days off, or the like, that immediately precede or follow

any two-day period taken or given regularly as a weekly rest period from one's work

the end of the week, esp the period from Friday night until the end of Sunday

Personally, whenever I stop doing whatever I am doing during the day on Friday, until whatever time on Sunday that I can't avoid being influence by the thought of what's going to have to be addressed on Monday---if there is anything to address.  And it's been that for me ever since I was a young kid.

I say it's any time after Wednesday.  :)

The week is like a circle...no beginning, no end.

maybe, depends on what you do then