Year system + counting years

What I will add is that you should probably have main calander and stick with it mostly throughout the story. Running several calenders at the same time sounds like it will just confuse the reader unless there's some good story reason to introduce it.

 

Eras in my story are based on major events and leadership through the timeline. For instance, when a group of intellectual mystics try to forge peace on the world, the Era of Mystics lasted a more than a thousand years and each one relinquished power once a major goal for the world was achieved by them (ie, to successfully incorporate the humans of the South into the system of improving the world), so counting years would look like m16 136. (m for mystic, 16 for the number of generations and major goalsthat have been accomplished, and 136 for the number of years (however long an orbital period takes for them) that the particular member has been in their position.)

But the mystic era is followed by the orphaned era, when much fell into disorder and the new kingdoms vied for power after the final generation of Mystics, so the era would look more like o286, and ect.

I don't know how this system compares to other systems, or even if it isn't just an overcomplicated mess for years to be written like this in history.

My recommendation is to identify what is important to the culture. For instance, the Christians adopted the Gregorian calendar, based on the sun, while the lunar calendar was chosen by the Muslims because of the significance of the Moon, and certain practices.

 

In general, the nations and societies in my world measure time relative to an event.

One nation measures since its founding, some measure based on the leader, there are city-states that measure the time since the Republic that once held them together dissolved, and so on.

I think that's a pretty common way to do things, especially if you don't have a society that takes over most of the civilized world at some point (ala Rome).

 

In my world they measure time from the time of the last re-creation of the world (the gods keep re-creating the world because they screw it up each time, according to their mythology)