Julian And Gregorian Calendar. The gregorian calendar and the julian calendar are both widely used calendars in the world, but they differ in several key aspects. The julian calendar is dated all the way back to 46 bc, during the time of julius caesar’s reign over the roman republic.

The following list attempts to give the year of conversion from the julian to the gregorian calendar for many countries and their constituent states, where necessary. Every fourth year an intercalary day was added to maintain synchrony between.