What's completely man-made is this account of the week, "Where the Five-Day Workweek Came From", in which long observation of four lunar phases of 7.4 days in length over millennia means nothing to an architect, who is, fittingly, cited as an authority, as in architects making stuff up.
The author, one Philip Sopher, an economics graduate from Princeton who should know his dates better, is completely ignorant of the Julian calendar reform of the Roman market day cycle of eight days to the more natural seven, which together with its other changes in 46 BC helped remove ever after in the West, not add, deliberate human meddling with the calendar, a common problem at the time of Caesar,
here:
“Seven days,” wrote Witold Rybczynski in the August 1991 issue of The Atlantic, “is not natural because no natural phenomenon occurs every seven days.” The year marks one revolution of the Earth around the sun. Months, supposedly, mark the time between full moons. The seven-day week, however, is completely man-made.
If it’s man-made, can’t man unmake it? For all the talk of how freeing it’d be to shave a day or two off the five-day workweek, little attention has been paid to where the weekly calendar came from. Understanding the sometimes arbitrary origins of the modern workweek might inform the movement to shorten it.
... At the very latest, the seven-day week was firmly entrenched in the Western calendar about 250 years before Christ was born.
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Little attention, indeed.