>>339884661
An interesting piece of study for those who are fascinated by this question are the Japanese E-Goyomi (絵暦); yearly lunar "picture calendars" made basically by committee in Edo during the Edo Period (~1600-~1868).
The boring part is that the lunar calendar needed to be adjusted for the phases of the moon, so the length of each month wasn't settled beforehand. The lunar calendar also had "intercalary months" that would show up every so often (a doubling of one of the months, Uruuduki, (閏月 literally "moons of an illegitimate throne"). They'd appear as something like "October, followed by Uruu October, followed by November" (十月、閏十月、十一月). As a result, every year they had to calculate and decide which months would be the longer months and which ones the shorter, as well as when the intercalary month would come..
The really interesting part is that the calendars that the committee made were just a picture. They'd hide symbols indicating which months would be longer that year and which ones would be shorter. And they'd just throw that at people and say "figure it out."
There are of course hundreds of these, and dozens for any given year (as multiple publishers/artists would make their own) and for hundreds of years many of them have been completely unreadable by modern people.
Here's one that has the symbols indicating the long months labeled.
Can you imagine if someone gave you the unlabeled picture and said "here's your calendar, bro"