Reading a little on Greek philosophy and have gone from 490 BC to 399 BC and realized I don't know how the Greeks would have counted the years, not knowing that AD was coming. What was their system of dates and did they count from some recognized point in the past?
This question is part of the FAQ. See also here. /u/sunagainstgold has previously described the development of the "Anno Domini" system here. You may also be interested in this podcast episode, feat. /u/Algernon_Asimov.