I just logged in and it shows it's still Summer and continues to remain Summer clear though till the 24th. No hint of Fall, much less an early one.
The event should be running and there are no restrictions as to how or where it's active. Not sure what server this is on, but I popped onto a random Live server and verified that the Bonuses event is running and displays on the calendar. Maybe relog and see if it shows on your calendar? Stone Cold Summer does run from 8/28 to 9/24.
I included the time on there to show when the screen shot was taken. Is it not Sept 13, 2019? I use time.nist.gov to set my computer's time. They're probably about as official as you can get. They say it's Sept 13, 2019.
