Was the "Week" Always 7 Days?

In reading this thread

I cam upon this comment by** APB**

The whole world now operates on the 7 day week (AFAIK), even though some Islamic countries and possibly others have different numbering of their years. My question is - how common was the seven day week among the various ancient cultures? Did the Egyptians, Greeks,ancient Chinese, native Americans, Incas, all have the concept of a “week”? What was the length of their weeks?

I am assuming that the dominance of the seven day week is due to the influence of the Judeo-Christian-Islamic tradtion. Any other ideas on that?


Take a look here, which says that the length of the week has varied from four to ten days in various cultures, and developed to provide the most suitable interval between market days.

Actually the week is the only unit of the calendar defined by humankind. All the others–day, month, and year–are based on the rotation and or revolution of the Earth or Moon. True, most months doesn’t exactly match up to the lunar cycle, being a bit longer, but still, the very word “Month” derives from “moon”.

So the quick answer to your question is no.

The French Revolutionary (or Jimm) calendar had 10 day weeks, as we discussed here:

The Mayan calendar did not have a concept of 7 day cycles being significant:


Without bothering to dig, I’m going to guess that many calendrical systems used by civilizations which do not trace their development to the Middle East do not set up 7 day cycles.

I recall being told by a student of such things that the Roman Empmire worked seven days a week with Holidays thrown in from time to time. In general a weekly day off is supposed to improve the productivity of the remaining six. Also The work day was from sunup to sundown.

As has already been pointed out, the intervals between market days was often the basis of defining weeks. In ancient Rome, markets were to be held every ninth day, which, since the market day itself was included in the count, results in an eight-day period referred to as nundinum, from novem, nine.

Actually, a week is part of the lunar cycle; it corresponds to phases of the moon (new, half, full, half, new) and thus is a quarter of the full lunar month. Actually, weeks line up better with the moon than months do.

While Judeo-Christian influence may be involved as well it is still a convinient way to split up the lunar month into smaller chunks.

In most (all?) Romance languages the days of the week are named after Roman gods, plus the sun and moon, maybe counted as gods. Perhaps these names are merely references to the planets named after these gods. On the other hand, in English and many other Germanic languages the days are named after roughly corresponding Norse gods, so maybe the gods themselves were meant (has the planet Jupiter ever been referred to as “Thor”?). If so, how did this come about if the seven-day week was adopted by Rome only with the adoption of Christianity? Was there a pre-existing system with other than seven days from which the names were adopted?