This isn't carved in stone by any stretch, but if you're wondering when Apple
will unveil its next generation iPhone model, word on the Web is that the Cupertino company is holding a press event on Saturday, September 12th, and at the time will be accepting iPhone 5 pre-orders in the United States. The actual release will take place more than a week later on September 21, 2012.
Un-named sources provided Apple fan site iMore with the above dates, and purportedly those sources "have provided iMore with accurate iPhone related launch dates in the past," so make of that what you will (in other words, don't bet the farm, but free free to gamble a dozen eggs or something).
iPhone pre-orders haven't always occurred on the same day Apple holds a press event, but with Samsung's Galaxy S III off to a fast start, it wouldn't be surprising for Apple to push its next generation smartphone out the door as quick as possible. There's been a ton of hype surrounding the iPhone 5, which is expected to introduce a larger size touchscreen than what's been found any previous iPhone model. It's also likely the new iPhone model will boast a 4G LTE radio, a feature that's sorely missing in the iPhone 4S.