Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
The only glitch I would be worried about is if your AA Exec Plat is quite recent. You definitely need to be Plat Pro or higher to be eligible for Globalist - that may well be defined as at September 12th instead of the point of receiving the email or registering.
Last year it worked fine for me, even when an IT problem meant that my 20th night arrived well after the 90-day period had ended.