Months In The Roman Calendar. The table below shows an educated guess about the length of the months in the years 47 bc (which was a typical roman year) and 46 bc (which was anything but typical). Birthdays, wedding anniversaries, and public holidays are regulated by pope gregory xiii’s gregorian calendar, which is itself a modification of julius caesar’s calendar.
In 45 b.c.e., romans modified their method of marking time to keep it in phase with seasons, but not require intercalation of an extra month. The original roman calendar appears to have consisted only of 10 months and of a year of 304 days.