Fossils form (for the most part) in bodies of water, because sedimentation occurs.

Fossilization needs to occur in places where the dead organism won't be disturbed, so a place in the ocean devoid of wave activity is required.

During most of the Roman Republic, years were named based on who had been elected to the consulship for that year.

All he could probably do to derive chronological information from the Olympic record was to consult a list of victors in the games for a rough approximation of the time when someone like Cylon, whose victory he mentions at 1.126.3 as evidence of the man’s eminence, had lived.

As his imprecise dating of Cylon to “former generations” reveals, he could not hope for much precision from this source. In Book 2.2.1 Thucydides also mentions that Pythodorus’s annual term as archon still had two months to run.

Instead, it tracked the number of years since the foundation of Rome: , lit. Not all ancient writers agreed on the same foundation year, however. So when that legend was invented during the Roman Republic the birth of the republic was a known fact and then 243 years were assumed as the time Kings ruled Rome (of which Romulus was the first)@user45891 that is however entirely offtopic to the question of "how is that year 'given'" - you're instead inferring the year from other sources. As I mentioned, different writers had calculated different years.

If one were to judge only from the first half of its title, Paul Christesen's Olympic Victor Lists and Ancient Greek History might seem to be aimed mainly at scholars who work on ancient athletics.