Here's when the iPhone 11 will probably be announced

Less than two weeks after the iPhone 11’s release date was seemingly revealed, an iOS 13 screenshot found within the latest beta version appears to confirm when Apple will be announcing its next-gen devices.
Apple seems to have chosen Tuesday, September 10
Spotted by iHelpBR, the screenshot is named “HoldForRelease” and features the Calendar app with the date clearly set to Tuesday the 10th. The month isn’t displayed but the day lines up perfectly with September, which itself coincides with Apple’s usual announcement schedule. Lending further credence is the fact a similar screenshot was found in one of Apple’s iOS 12 beta releases last year which showed September 12th, the date that was subsequently confirmed for the iPhone XS and iPhone XR introductions.
Considering the iPhone 11 series is now expected to debut on Tuesday, September 10, pre-orders for Apple’s upcoming trio of devices will likely commence on Friday, September 13. The actual launch, on the other hand, should happen on Friday, September 20. This coincides perfectly with the previously reported release date.
On an unrelated note, an iPadOS 13 screenshot showing the same date was also spotted. Apple has been rumored to be planning the debut of a new 10.2-inch iPad alongside its next-generation iPhones and this image suggests this will indeed be the case.