The Gregorian Calendar, named after Pope Gregory XIII, was created in 1582 to correct errors in the Julian Calendar that became apparent over time. The Julian Calendar was actually 10 days ahead of where it should have been, and this discrepancy was corrected with the new Gregorian Calendar, which is the most widely used in the world today. It consists of 365 days in each year, with a 366-day leap year every fourth year. The calendar is broken down into 12 months. Unlike its predecessor, the Gregorian Calendar does not count the last year of each century (years that end in '00') as a leap year unless the number of the year is divisible by 400.