Why doesn't Eusebius of Caesarea even mention the Julian calendar in his Chronicle? Chronicle by Eusebius of Caesarea covers period till A.D. 325. Armenian translation of Chronicle ends with the following passage:

Now it is appropriate for us to append a list of the emperors of the Romans, starting from Julius Caesar. We shall mention the consuls for each year, equating [these dates] with the Olympiads.

Not that the Julian calendar

. . . . became the predominant calendar in the Roman Empire and subsequently most of the Western world for more than 1,600 years until 1582, when Pope Gregory XIII promulgated a minor modification to reduce the length of the average year from 365.25 days to 365.2425 days and thus corrected the Julian calendar's drift against the solar year. Wikipedia:JulianCalendar

I found it very strange that Eusebius names Julius Caesar but does not mention his calendar which is supposed to be in a wide use at the time of Eusebius' writings.

  • 1
    There is no contradiction between the two cites that you quote. The essence of Caesar's reform was that year is 365 days, except the leap year which is 366 days, and every fourth year is the leap year. The question how to count years is a separate question, and Eusebius includes the list of emperors and olimpiads for comparison with other sources. For long time after Caesar, the years were counted using Roman consuls, emperors olimpiads etc.
    – Alex
    Feb 25, 2021 at 17:02
  • When you write numbers, do you bother mentioning that you are using Indo-Arabic numerals?
    – C Monsour
    Feb 26, 2021 at 7:34
  • @CMonsour It seems Eusebius bother. From Chronicle: "For example, the ancestors of the Egyptians spoke of a lunar cycle, that is, a month contained 30 days, which they referred to as a year."
    – zer0hedge
    Feb 27, 2021 at 11:54
  • You don't seem to understand. He's remarking on other people's calendar, not his own, when he says that. Just as you would call Roman numerals Roman numerals but not name the ones you use.
    – C Monsour
    Feb 27, 2021 at 18:17
  • The years are, obviously, those after Caesar; see list of Roman consuls for correspondence with the Anno Domini era, which was invented more than two centuries after Eusebius. Perhaps a better question would have been why he doesn't reference the Diocletian era, on which the former was based; but even that is trivial to answer: it was a recent concoction, thus useless for the ancient events detailed in the Chronicle.
    – Lucian
    Apr 23, 2021 at 18:55

1 Answer 1


Julius Caesar established the Julian calendar as the official calendar of the Roman government, army, and religion and the civil calendar to be used by Roman citizens. Many cities and provinces in the Roman Empire also came to use the Julian calendar.

There is a difference between a calendar and a calendar era. A calendar era is a moment in time that later years are counted from. It is possible for different calendars to use the same calendar era, and for people who use the same calendar to use different calendar eras.

Various parts of the Roman Empire used different calendar eras. The Romans themselves mostly didn't bother with numbering years, but mostly named each year after the two consuls for the year. So they would refer to a year as the year of the consulship of X and Y, naming the two consuls.

A less often used method was to use the foundation of Rome as the calendar era. Roman historians suggested several dates for the legendary foundation of Roman, and the year we call 753 BC eventually became the official date for the founding of Rome.

Greeks often used the four year long Olympiads for date events, which would be dated to the ____th year of the ____ Olympiad. The first Olympiad began in 772 BC.

It was also common to date events by the regnal year of the current emperor.

And many different localities in the Roman Empire used different local calendar eras to date events, while using the Julian calendar or a local calendar.

If Eusebius of Caesarea dated events only to the year, and not to the precise date, he would have no need to compare and mention different calendars, since most dates he worked with would have been given in calendars that used years of approximately the same length.

  • 1
    Around the time Eusebius was writing, there were some locations where people were counting regnsl years of Diocletian even beyond his abdication
    – C Monsour
    Feb 26, 2021 at 7:40
  • That would be 776 BC.
    – Lucian
    Apr 23, 2021 at 18:44

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