> Apparently it's unlikely to be an accident, but it's a very ancient connection, via the chinese, who have in more recent times ditched the system. China is a

> Apparently it's unlikely to be an accident, but it's a very ancient connection, via the chinese, who have in more recent times ditched the system. China is a relative latecomer here and typically lags these types of ancient civilizational innovations, with the oldest being Mesopotamia and Egypt. In China, the seven day week was adopted in the late 4th Century A.D. in the Jin dynasty roughly 3000 years after it was adopted in Mesopotamia. There are two theories as to the origin of the seven day week, one that it started in ancient Babylon and another that it started in ancient Egypt. The concept of a "week" is directly tied to the concept of a sabbath (a special holy day to mark the end of the week). This, in turn is related to Babylonian numerical systems -- they had a base 6 system corresponding to 6 days of work followed by the religious day, and hence the origin of our seven day week. Interestingly, unlike in judaism where the seventh day is considered one in which work was forbidden as God rested on that week, in Babylonian tradition, the seventh day was considered unlucky for work and thus work was to be avoided. It is a fine line separating these different notions of a Sabbath and thus of the week. Another speculated origin for the week was via lunar observations -- e.g. a quarter phase of the moon corresponding to a half-moon either waxing or waning with a lunar month being roughly 29.5 days, so 1/4 of that would be 7.4 days. But there are different ways to divide this -- e.g. a sequence of 7 day units followed by a sequence of special days tacked at the end or some other combination. You actually see these types of divisions in some ancient Babylonian calendars. But with a base 6 system, there are some nice divisions, e.g. 6 days of work followed by the holy day = 1 week 4 weeks followed by a holy day at the end = 1 month the residual .5 day, can accumulate so that after 12 months, 12*.5 = 6. 6 special days to be added at the end of 12 months. In the ancient past, you had different regions practicing their own calendar system and one of the first innovations of the first (known) empire in Mesopotamia was the standardization of weeks and months as different cities were brought into the Sumerian empire. Sargon I of Akkad is said to have standardized the week by ensuring that the different cities he conquered were synced up and observed the same set of extra holy days in what is the first (known) empire https://www.tandfonline.com/doi/pdf/10.1179/030801882789801278 https://www.tandfonline.com/doi/pdf/10.1179/0308018827898012... However there is some linguistic evidence that the Sumerians merely borrowed the concept of a week from the Akkadian civilization, so the earlier Akkadian civilization is believed to have held the concept of a week first. Once you have the notion of a week, it is not hard to name it after the sun, moon, and 5 celestial planets, as these were the primary astronomical phenomena. You can see these names in ancient languages here: https://www.hermetic.ch/cal_stud/hlwc/why_seven.htm https://www.hermetic.ch/cal_stud/hlwc/why_seven.htm