Two sources talk of Apple iPhone event around September 12th, part sales back it up (update: one more clue)

Apple's plans for its next iPhone refresh may be getting very tangible, very quickly. It all started when iMore heard that Apple was preparing to hold an event unveiling the new hardware on September 12th, with a launch the following week on September 21st. Although the relative newcomer to the iPhone release date rumor game is still building its track record, that claim may have just gotten some extra meat: AllThingsD is joining in the chorus and touts its own sources pointing to an event in the same timeframe. While it's almost a month earlier in the year than Apple's iPhone 4S event was in 2011, it's supported by an Apple filing with the SEC showing a sharp uptick in supply purchasing during the spring, which it would need to start production for the fall. All of it is still rumor, of course, but past experience suggests that iOS fans may want to plan any September camping trips for the Apple Store line late in the month, not Labor Day weekend.

Update: Jim Dalrymple at The Loop, who's well-known for his accurate one-word confirmations and denials of rumors, just posted his trademark "yep."