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.