So we use BC and AC . My question is did ancient civilizations count years and based on what they counted years? What was the most used counting-system used around the globe . And did different regions use different counting-system from one another?
I asked to many questions but hope you answer.
I recommend these previous answers in the FAQ as a starting point: they'll cover the general topic. The short answer is: not all of them counted years, but some did; local eponymous era systems were the most common form of reckoning; and yes, everywhere had its own era system. I'm sure if you have more specific questions there'll be someone keen to post an answer.