Why do clocks rotate in a "Clockwise" direction?

I realize only the older, pre-cellphone crowd will understand what I mean since digital clocks don’t rotate at all.
But why do they rotate in that particular direction? Was it just an accident of invention? Is it some sort of psychological need? Does it relate to the rotation of the Earth? Were some clocks made that went the other way before it was standardized?
Where did the twenty four hour day come from? Why not twenty hours? Why do we divide it into two twelve hour segments? Why not four six hour segments to balance the four seasons? Why divide it at all? Could we ever go to a metric time system?