So in all the names for the days of the week originated from the seven known "planet's" : Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn.
At the time, the order for the relative distances of these planet's from furthest to closest was:
Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
The hours of the day used to be given these names, in this order. Which means that they were all used three times in a day, with three used a forth time. When a new day began, they did not start over, but from where they left off. If the last hour of a day was Mercury, the first hour of the next day would be Moon.
So the pattern goes like this
Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars
Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer
Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup
Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven
Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat
Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun
Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon, Sat, Jup, Mars, Sun, Ven, Mer, Moon
Thus when you name the days after the hour they begin with, in order you get: Sat, Sun, Moon, Mars, Mer, Jup, Ven
