How Did the Years Before Christ Count?

A question that came to mind these days and I was curious.

After researching a little on the internet I discovered that there was no standard count among peoples, which makes a lot of sense for the time.

And that only in 525 AD we had the Christian standardization of the calendar, when a pope resolved to unite the Catholic church around the world in the same count.

Until then each people counted the years in its own way, usually based on the seasons of the year due to agriculture. It was from summer to summer.

The Egyptians began to count around 3000 BC, which shows us the degree of evolution of this people. For the Romans, the founding of Rome in 753 BC was the beginning of the count and for the Greeks the initial mark was the first Olympics, about 2500 BC.