Julian calendar

A calendar instituted for use in the Roman Empire by Julius Caesar from 46 bc. There were twelve months in a year and three years of 365 days followed by one of 366 days, giving an average of 365.25 days. Since this is 11 minutes 14 seconds longer than the tropical year, which governs when the seasons occur, the seasons gradually moved in relation to the civil year. Because of this, the Gregorian calendar was introduced from AD 1582.