Olympic Dates

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These pages give access to conversion tables in Excel format, with copies in HTML format and in CSV format, useful for determining the Julian equivalent of years dated according to Olympiads during the Ptolemaic era. This system was used by Greek historians to provide a common frame of reference to reconcile historical dates given in many different local calendars. It is particularly important for interpreting the regnal years attributed to the Ptolemies by Porphyry, as transmitted through the works of Eusebius.

This page provides analyses of three topics related to the Olympiad system:

Julian synchronisation of Olympic years

In order to convert a specific Olympic year to a Julian year (or pair of Julian years), we must first establish the general relationship between Olympiads and Julian years. Fortunately, this is very straightforward.

The base synchronism is given by Diodorus Siculus, who dates his years according to the Athenian archons, the Roman consuls, and, every fourth year, by Olympiad. By this system, Diodorus 20.5.5 reports a solar eclipse in the year of the archon Hieronmenon, corresponding to Ol. 117.3, which must be that of 15 August 310. This gives us Ol. 117.3 = 310/09, from which Ol. 1.1 = 776/5. The resultant Olympic dates for well-known events, such as the death of Alexander III, dated to Ol. 114.1 = 324/3, shows strong consistency with this date.

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