Timeline

[AEIOU]

You asked for examples and I made some up.

Me, I'm sticking to a Gregorian derivative. My head hurts enough already without twisting it in double helixes. I think Planescape and Traveller type games will benefit from flexibility.

Rob has mentioned that the calendars will interoperate even if they have different baselines. So your calendar could have a date that everyone lives their lives by while also being able to track for lunar activities or tides or holiday or whatever. For a real world example, both Gregorian and Aztec would be doable and inter-relate with one another even though they are dissimilar.

[MNBlockHead]

I'd be happy with any non-arbitrary calendar support. Historically, there were many calendars, such as old Roman Republic, where certain units could be arbitrarily changed E.g., the pontifex would call out ("calare"- the word "calendar" is derived from this custom) the beginning of the month. It originally had 10 lunar months of 304 days an an uncounted winter gap.

I was looking into using an Etruscan calendar systems since one of my realms is based upon the parlor game of wondering what would happen if, instead of the Romans conquering and absorbing the Etruscan culture, if the opposite happened and the Etruscan's grew into an empire. It was supposedly an Etruscan who gave Rome its first calendar (which probably derived from the Greek lunar calendar, which probably derived from the Babylonian). But the ancient, somewhat arbitrary lunar calendar of the Etruscans/Early Rome is just too difficult for me to use in-game and convert to other calendars. So, I just assumed that the Etruscans would have eventually evolved their calendar into a solar calendar, somewhat like the Julian.

Even after adopting a solar calendar with no winter gap, the Pontifex Maximus could arbitrarily alter the calendar—and often did so to extend (or reduce) the term of a public official. This is another practice I have decided to not to incorporate. Ancient societies had full-time clergy and scholars responsible for managing calendars. I don't have that luxury.