Of Hellanicus, the Greek logographer, who appears to have lived through the greater part of the 5th century B.C., and who drew up a chronological list of the priestesses of Here at Argos; of Ephorus, who lived in the 4th century B.C., and is distinguished as the first Greek who attempted the composition of a universal history; and of Timaeus, who in the following century wrote an elaborate history of Sicily, in which he set the example of using the Olympiads as the basis of chronology, the works have perished and our meagre knowledge of their contents is derived only from fragmentary citations in later writers.
In the history of Babylonia, the fixed point from which time was reckoned was the era of Nabonassar, 747 B.C. Among the Greeks the reckoning was by Olympiads, the point of departure being the year in which Coroebus was victor in the Olympic Games, 776 B.C. The Roman chronology started from the foundation of the city, the year of which, however, was variously given by different authors.
Of the three ancient eras above spoken of, the earliest is that of the Olympiads, next that of the foundation of Rome, and the latest the era of Nabonassar.
The Olympiads were not in current use till about the middle of the 3rd century B.C., when Timaeus, as already mentioned, set the example of reckoning by them.
In referring dates expressed by Olympiads to our era, or the contrary, we must therefore distinguish two cases.