Are there any non-lunar, non-solar calendars?

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?

Use the one that Unix uses which just counts the milliseconds since an arbitrary date in the 1970s

Another option from an even more obscure programming language: MUMPS

The ancient Egyptians had a 365 day calandar that wasn’t exactly solar. It was based on the rise of Sirius and the yearly Nile flood.

Julian Day.

Interesting, but I guess I am looking for a system that is a little more fleshed out, with specific divisions.

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.

I’ve found an online Aztec calendar converter that you could use.

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.