Countries which have not adopted the Gregorian Calendar
Can you guess the countries which don't use this calendar (red), use other calendars alongside the Gregorian calendar (orange) or have a modified version of the Gregorian calendar (blue)?
According to this picture: http://i.imgur.com/rEepIt9.png
NOTE: The official calendar in China is the Gregorian calendar, but the traditional Chinese calendar still plays an important role there