As an example, let's say a Roman primary source gives us the only known reference to an event as having occured "300 years in the past". Now, Roman dating was fairly chaotic. Even after they went from 10 month years to 12 month years, they would periodically insert a 13th month. So simply multiplying the number of years by 5/6 wouldn't work obviously. Rarely would a "year" for the Romans correspond to the solar year, or equal out to 365 days. I assume this is a problem for historians of every culture, not just the Romans. So can anyone here give me an example of how historians are able to give objective dates for certain events?