The year 1582 involved conversion to the Gregorian calendar. Year 1582 began as a common year starting on Monday of the Julian calendar, and continued as normal through Thursday, October 4. However, the next day became Friday, October 15 (like a common year starting on Friday), in the Catholic countries: Italy, Poland, Portugal, and Spain. Other countries continued using the Julian calendar, switching calendars in later years.

Events of 1582