Planetary Hour Origin
No one is certain as to how the idea of planetary hours came into being. The only thing that is certain is that it is responsible for the order of the days of the week and therefore predates the Bible and the Genesis story for the creation.
The ancient Chaldeans are said to have arranged the planets in this order (now called the descending Chaldean order):
Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
This is the order of the passing of the planetary hours. After the Moon hour, a Saturn hour starts the cycle over again. Planetary hours are an equal division of the time between sunrise and sunset and again from sunset to sunrise, by 12. This makes 168 hours in a week.
At some point in the distant past, by what philosophical reasoning is unknown, a sunrise or sunset defined the first planetary hour in history. It has run on uninterrupted in this manner (as far as I know) longer than recorded history.
Count the hours out and you will see that starting with any day of the week, taking the first hour of the day, after 24 hours have passed, the 25th hour becomes the ruler of the next day. For instance, take Saturday, the first hour is assigned to Saturn (which is why it is called Saturday). The 25th hour from this hour is a Sun hour. This becomes a Sunday. The 25th hour from that Sun hour is a Moon hour. This becomes Monday. The 25th hour after the Moon is Mars. This becomes Tuesday or "Mardi" in French. The 25th hour from this Mars hour is Mercury. This becomes Wednesday. The 25th hour from that Mercury hour is a Jupiter hour. This becomes Thursday or "Jeudi" in French (meaning Jovial). The 25th hour after Jupiter is Venus. This becomes Friday or "Vendredi" in French.
