Ok, so during a bit of “boy time” me and Chix were pondering the world and trying to figure out why there were 24 hours in a day… not sure how we got onto the subject but the answer (if google is to be believed) is as follows:
At which point Bryan crooked his right thumb to touch the base of
his right index finger (please follow along and do it, too), and said,
in much the same way as a Sumerian might have, 4,000 years ago…
"One."
He then moved up a notch – see that? Each of your fingers has three
distinct segments. I never really noticed that! – and, touching now
the middle segment of his right index finger with his right thumb, he
said… "Two."
I think you may sense where this is leading. By the time your right
thumb has counted each of the three segments of his neighboring four
fingers, you’re up to 12.
Long before people were reading with their lips, one imagines, they
were counting with their fingers.
So a day was divided into 12 segments, called hours; and, too, the
night.
Source
So there you have it, QED