Hi as in the western world practiced we use a calendar that is supposed to start with the birth the so called Son of God. In Islam they do the same just with Mohammad leaving Mekka. But before that, calendars were already used. So I'm assuming that the "older cultures" also used some kind of amazing event as a startpoint of their calendars, so what are some of those? Doesn't matter to me if roman calendar, buddhist calendar, jewish calendar or whatever. And at what year was the roman calendar when Jesus was born ?
So I'm assuming that the "older cultures" also used some kind of amazing event as a startpoint of their calendars
That would be an unsafe assumption! Different places in antiquity used a whole bunch of systems, and only a minority of them measured years by counting from a specific event. Most of them referred to a year by specifying who was in a specific local office at the time (e.g. consul, archon, king, emperor), and/or how long they had held that office (e.g. "in the fifth year of So-and-so's reign"). The Romans at the time referred to 1 BCE as "during the consulship of Cossus Cornelius Lentulus Gaetulicus and L. Calpurnius Piso". More details in this thread.
Calendar eras that measure time from a specific moment were used to some extent by historians in antiquity, but not for general usage. With one or two exceptions, they only started to be used on an everyday basis with the spread of the Abrahamic religions.