The Ancient Romans used an eight day week. They also used really bad calendars.
Tomorrow is Tuesday. Proof: I’m having tacos tomorrow. QED.
Well, except for weeks, which are almost entirely artificial. But the other two are recurring astronomical events, as is the year.
A month was basically the time it took the moon to go through a complete cycle of phases, or as we say in our more enlightened times, to complete its orbit around the earth. To make up the deficiency a day or two was added to eleven of the twelve months, and February lost a day or two just to make everything come out nearly “right” (i.e., a year being twelve months long).
I keep up with it so I’ll know when my birthday is. 
I’ll let you all in on it when it’s time. Gifts are appreciated, of course.
We’ve already got it. In fact, not only “thirds” but “fourths”, “fifths”, etc., already exist as technical terms in English to refer to those fractional places in any sexagesimal (base-60) units, not just time units. Here’s an example from a navigational table in the 1760 Astronomia Accurata; Or the Royal Astronomer and Navigator by Robert Heath:
Well, that explains months, but what about the rest of them?
:dubious: Ai-yi-yi. No, a lunar month is a synodic cycle, i.e., a return to the same relative positions of the moon, earth and sun. Not a complete revolution of the moon in its own orbit or sidereal cycle.
The former takes slightly more than 29.5 days and the latter less than 27.5 days, so you can’t really use them interchangeably.
The planning but makes sense and at least it’s not out of thing air but it has solid backing.
I guess I have been interactioning with too many folks who “question everything”
Culture and civilization is broadly speaking the result of innumerable ideas that humans make up or come up with to satisfy their needs and cravings. Other animals pretend too but to a smaller extent. Due to their superior capacity of reflection, human beings can entirely reshape the social metabolism of their communities so that they can better control the environment and thus they eventually wind up living in an impossibly intricate web of conventions whose architectonics keeps them together as a group and controls them as individuals.
;)Far out, man!:D:cool:
I was so slick, man…I slid that one past myself, man.:smack:
You’ve met my hippy friends?
‘Five minutes’ can mean anything up to half a day…
I hear ya… and also … why can’t we fill the world with silly love songs? What’s wrong with that? I’d like to know.
I thought it was Mussolini who invented that. Or that other guy-- what’s his name.
Have you ever been to the Middle East?
In the Age of Trump, every day is garbage day! 
Excuse me, but I’m going off in search of something to drive that godawful song from my head. :eek:
My apologies
Maybe this oneis more appropriate?
<nitpick> Tomorrow is Wednesday.
Well, at least the French Revolutionary Calendar never caught on (lousy Thermidor weather!).
Ahhhh, Proof: Margarita special at my favorite bar. QED