Created in the 8th century by Romulus, the founder of Rome.
The calendar was 10 months and 304 days.
The new year was on the vernal (spring) equinox, or March 20th.
Created in 46 BC by Julius Caesar with the help of astronomers and mathematicians to combat previous calendars falling out of sync with the sun.
To honor Janus, the god of beginnings, January 1st became the first day of the year.
Introduced in October 1582 by Pope Gregory XIII
A modification of the Julian calendar, which did not accurately reflect the cycle of the sun.
Used by Catholic churches to determine the date of Easter.
There are a few countries that do not use this calendar to this day.