Ancient roman dating calendars
This script creates a calendar converter that can convert five different units at one time; that is actually converting between the Gregorian Calendar, Julian Calendar and Julian Date, and translating those into the Roman and Latin versions of the Julian Calendar.
The Roman calendar changed frequently with varying year lengths and so the days and months are not valid before 8 AD and are only presented for illustration purposes.
Between 45 BC and 8 AD, the leap years in the Julian calendar do not follow the standard rules and the following leap years are implemented in the above algorithm: 45 BC, 42 BC, 39 BC, 36 BC, 33 BC, 30 BC, 27 BC, 24 BC, 21 BC, 18 BC, 15 BC, 12 BC, and 9 BC.
Gregorian Calendar The Gregorian calendar has leap years every four years, like the Julian calendar.
The information provided below the converter is from our page sponsor and is very helpful to the details and understanding of calendar differences.
The Roman calendar was introduced circa 750 BC and so dates before 753 BC are not allowed.
(anno urbis conditae - from the year of the founding of the city). Unfortunately, the leap years were not correctly implemented until 8 AD - a mix up meant they came every third year instead of every fourth until 9 BC and then Emperor Augustus scrapped leap years until 8 AD.
Note that there is no zero year and the year 1 BC is followed by 1 AD.
However, the Gregorian calendar skips leap years when years are divisible by 100 (but not by 400) To ensure the vernal equinox of the Gregorian year falls on March 25th, ten days were 'removed' from the Gregorian calendar and the 4th October 1582 (Julian Calendar) was followed by 15th October 1582 (Gregorian Calendar).