The Calendar of the Christian world began a century before Jesus Christ, by Roman Emperor Julius Ceasar.

This Julian calendar introduced the notion of leap years, however, there were too many and by 1582, the calendar was ten days out of sync with seasons, and this would only become worse.

The name of the current Calendar: The Gregorian Calendar bears its name due to Pope Gregory XIII. He suggested to drop out three leap years in every four hundred years. The calendar will not fall out of step until 5000 AD. A small fix, will keep it in tune until 15000 AD.