Some destinations have a "90/180 rule" which says you can come and go but you must not spend over 90 days out of any 180 days in the area. A recent question asked by a new contributor concerns this ...
Can immigration authorities make cross checks between multiple passports of the same (German) person?
I have the following specific case but it would be nice to have a general answer if one does exist: A fellow German traveler just spent 3 months in Turkey on his passport. He just then left to ...