If you’re reading this, you should be familiar with the seven-day week starting on Sunday or Monday and followed by Tuesday, Wednesday, Thursday, Friday, Saturday and so on. But there have been instances in history and other cultures where an eight-day week was observed.
For example, the Romans adopted the eight-day week from the ancient Etruscans who called it the nundinum. The Romans also tried to use a seven-day week alongside it but the week cycle we know today won out and was officially established by Emperor Constantine in AD 321.
Their enemies, the Celts, were said to use an eight-day week based on periods of darkness which led to words like wythnos literally meaning eight-day week in Welsh but is now used to refer to a seven-day week.
And in the current day, Theravada Buddhism in Burma use an eight-day week with each day associated with a compass direction, a planet, and a totem animal from the Mahabote zodiac (you can even find your zodiac sign).
Outside of that, I found a personal project for an octonary week by Joe Scanlan who remapped his own calendar in the 90s:
This calendar really suits me, and now I am interested in sharing it with other people, to see it it might also suit them. This is the part of the project that remains unrealized. Here’s why: the current 7-day week is based on the seven “planets” that are visible to the naked eye: the sun, the moon, Mars, Mercury, Jupiter, venus and Saturn. In order to have an 8-day week, we need to have another planet made visible In the heavens, to correspond to the extra day. This requires either constructing an artificial planet (a satellite) and placing it in orbit in our solar system; or some how altering either Uranus, Neptune or Pluto so that one of them would be visible to the naked eye from earth. Perhaps a giant lense or mirror could be built on one of them, the reflection of which would distinguish the planet from the other stars in the sky. This would make the global introduction of the 8-day calendar much easier, since its celestial logic would be evident to anyone looking at the night sky.
And there’s a 1999 article in The Independent by Michael Hager (now a Member of Cabinet at European Commission) advocating for an eight-day week, calling the week an “arbitrary unit” of measurement:
By itself, a reconfiguration of the week from seven to eight days, retaining the typical five working days, would cause a lesser drop in productivity than would shifting from a five- to a four-workday schedule in a seven- day week. For societies that adhere to a five-day working week, the insertion of an eighth day would reduce the number of potential work days from 260 to 228 (on average), since the number of weeks in a year would fall from 52 to 45.6. On the face of it, this implies an annual loss of productivity of about 12 per cent.
[…]
With three days instead of two between work weeks, both women and men would find it easier to juggle jobs and family, and everyone would have more opportunity to enjoy the arts, hobbies, sports and entertainment.
I like the idea of a 3-day weekend but not so much from the perspective of adding an extra day for the sake of maintaining productivity. But hey, that’s European politics for you!