I was thinking that is a safe date, but wouldn't I have 44 days left over still, so does September 1st still allow me 90 days?
That's what my calculations show, after searching for details on the rules:
You can stay 90 days in any 180-day period within the Schengen area.
When applying this rule, the following aspects should be taken into account:
• The date of entry is considered as the first day of stay in the Schengen territory;
• The date of exit is considered as the last day of stay in the Schengen territory;
• The 180-day reference period is not fixed. It is a moving window, based on the approach of looking backwards
at each day of the stay (be it at the moment of entry or at the day of an actual check, such as inland police
control or border check upon departure);
• Absence for an uninterrupted period of 90 days allows for a new stay for up to 90 days.
You stayed from day 108 to day 153, which is 153-108+1=46 days; September 1 is day 244, so that when you've been there 44 more days, on day 244+44-1 = 287 (Oct 14), the previous 180 days will include only 44 days in the region, and you have another 46 days to stay, until day 244+90-1=333 (Nov 29). (The inclusive dating is a little confusing, but I think I got that right.)
One of several "Schengen visa calculators" agrees with me (though it makes a disclaimer, as I do). You may want to check with someone who knows the rules, rather than just someone who knows math and had never heard of the rules.
On the other hand, my searches revealed that the rules will be changing soon.
