varies according to local conditions. Mine tends to start at about 3, as I'm a night worker; QM doubtless keeps more sensible hours. And I suspect it's different in winter and summer, and possibly Down Under, where jobs often tend to be 9 to 5 rather than 10 to 6. Moral: if you arrange to meet someone at the end of early afternoon, it might be as well to check where they come from.
Logic: if early is followed by mid, there must be a late too.
So divide afternoon in to three.
Say it runs from noon to 8pm (followed by night and morning, usually.
So it's eight hours long, ie each third is 2 hrs 40 mins.
So early = 1200 to 1440
Mid = 1440 to 1720.
Late = 1720 to 2000.
OK? Give in?