Transcript: Every human culture has felt the need to subdivide time. In addition to the seasons, which follow from the Earth's motion around the sun, and months, which are tied to the lunar cycle, almost every culture has divided time into weeks. "Week" comes from the old German word meaning "to change." Weeks have had different numbers of days in different cultures through history. The modern tradition of a seven-day week actually dates back to the Babylonian times.  The word “Sabbath” is a Babylonian word meaning "to rest."  On the original Sabbath day, only the ruler rested, while the other people had to work.  The idea of a weekend is a modern invention only a few hundred years old.  Why does a week have seven days?  Because there are seven visible, moving objects in the sky: the Sun, the Moon, and the five nearest planets.  If you consider the names of the days of the week you will see that.  However, you usually have to go into a Romance language, French, Italian, or Spanish, to see it clearly.  Sunday, obviously, the day named after the Sun.  Sun worship was big for ancient cultures. This is the day of rest.  Monday, named after the Moon. Tuesday, not obvious, but in a Romance language, obviously associated with Mars.  In the English culture, this word came from the Norse god Tue. Wednesday, in a Romance language, you will see that relates to Venus.  Our name of Wednesday comes from the Norse god Woden.  Thursday: in Romance languages you will see this relates to Jupiter.  In our language, it comes from the Norse god Thor.  Friday relates to Mercury, in our language, the Norse god Frig.  And Saturday, is of course, for Saturn. Seven has always had mystical significance for cultures throughout history, so the number of days of the week relates to mysticism and the ancient practice of astrology.