Have wondered this for quite some time. Schools occasionally teach alternative calendar systems but I’m yet to encounter alternate popular year naming conventions throughout history, wondered if anyone could shed some light?
This question is asked often enough to be the very first one in our Very Frequently Asked Questions page. There is always more to be said, of course, but while you are waiting for fresh answers, you might like to review that response, led by u/sunagainstgold. Just below that link, u/400-Rabbits examines the problem of what dating systems were used before BC/AD became so commonplace.