I am looking into adopting an alternative calendar system for personal use. Preferably, one that would be as eccentric as possible, but have been in used in some real capacity in the past. Which leads me to ask:
It seems that almost all calendar systems are either solar, lunar or lunisolar. Are there any fully documented calendar systems that exist outside of these realms?
How about the Aztec tonalpohualli? It’s a 260-day calendar. It’s not clear at this point exactly what it was based on. But it doesn’t line up with the year, so it’s not solar. It was divided into 20 periods of 13 days each, which isn’t lunar.
You could always try to revive the French Republican Calendar. Maybe it’ll catch on this time. It is still “solar” however in that it tracks years, like the Gregorian.
The “arbitrary” date is not so arbitrary: it’s January 1, 1970. Also, the unit used is normally seconds.
IIRC, the Aztex? Myans? somebodies had a calender based upon the movements of Venus. It was pretty damn long and complicated and IMO quite sophisticated too. Once hearing about it, you realized these guys had to have been taking detailed notes and thinking about this for probably centuries to even come up with it.