It is likely that the seven-day week as we know it has run uninterrupted
since the time of Moses, and possibly much longer than that.
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The Mayas used a 13-day and a 20-day week, both at the same time.
The ancient Egyptians, the ancient Chinese, and
the revolutionary French used ten-day weeks.
The Incas used nine-day weeks.
Pre-imperial Rome used eight-day weeks.
The Sumerians and the Hebrews used a seven-day week.
The Vedic Indians used a six-day week.
The early Soviet Union tried five-day and six-day weeks.
The seven-day week had spread to Rome by the 1st century BC, but was not
made official until the reign of Constantine.