Not only that, but the Roman calendar was a mess from whole end of the Republic going on for the last ~100 years. The dates for some of the events listed in the

Not only that, but the Roman calendar was a mess from whole end of the Republic going on for the last ~100 years. The dates for some of the events listed in the Roman civil wars of Caesar had drifted from solar time pretty badly at the end (40'sBCE) and were off by month from the solar year. (The Romans has used a lunar calendar previously) In fact, members of the priesthood who determined the festival days that would bring the lunar calendar in sync with the actual solar time were often bribed to extend the year which would allow the consuls longer times in office. One of the first things Caesar did when he became the sole ruler of Rome was to reorganize the calendar around the solar year. He did so with the help of a Greek Astronomer from Alexandria. I believe the Greek astronomer made some faulty calculations regarding leap years, which is why the Gregorian calendar was instituted to fix the mistake in the 1500's.