Map of calendars officially used around the world.
  Countries which have adopted the Gregorian calendar.
  Countries which use a modified version of the Gregorian calendar.
  Countries which use other calendars alongside the Gregorian calendar.
  Countries which have not adopted the Gregorian calendar.
Own work, based on File:BlankMap-World.svg and Imgur calendar map. Note that Saudi Arabia switched to the Gregorian calendar in 2016.
Nederlandse Leeuw