Year 1582 (MDLXXXII) was a common year starting on Monday (link will display the full calendar) of the Julian calendar, and a common year starting on Friday (link will display the full calendar) of the Proleptic Gregorian calendar. However, this year also saw the beginning of the Gregorian Calendar switch, when the Papal bull known as Inter gravissimas introduced the Gregorian calendar, adopted by Spain, Portugal, the Polish–Lithuanian Commonwealth and most of present-day Italy from the start. In these countries, the year continued as normal until Thursday, October 4. However, the next day became Friday, October 15 (like a common year starting on Friday), in those countries (France followed two months later, letting Sunday, December 9 be followed by Monday, December 20). Other countries continued using the Julian calendar, switching calendars in later years, and the complete conversion of the Gregorian calendar was not entirely done until 1929.