I have been to Schengen between 10/05/16 and 23/06/16 (45 days). Now I wish to go back for 90 days. Do I have to wait for the beginning of new 180 days period? Or can I enter Schengen about 40 days before the end of the first one (let's say beginning of October) and then stay for 90 days? Can I go between 1/10/16-1/1/16?
I mean that way I would never overstayed in the last 180 days because every time a new day of my new staying is added, an old one is expired of the 180.
Is there any official representative I could email to have an official answer?