Kodawarisan, a Japanese website, is reporting that Apple's Fall Event, which previously focused on iPods but will likely include the iPhone 5 announcement this year, is scheduled for Wednesday September 7, 2011. The rumoured date jives well with previous years.
Apple has always targeted early September for their Fall Events. Last year, the Fall Event was held on September 1. In 2009 and 2008, it was held on September 9. So it does make sense from a historical perspective. This year is a little different though because it will be the 10th anniversary of the 9/11 attacks on September 11th. Holding the iPhone 5 announcement a few days before the tragedy's anniversary might divert people's attention that would be better placed with the US. But who knows, we've balanced it in the past.