According to iPhone Italia reliable source, that iPhone 5 will be released on the United States by September 5, then it will be released internationally after one month (October 5).

“From a very reliable source we learned about the business strategies of Swisscom relation to the release of iPhone news has caused a 5 and particularly our interest: the Swiss provider will have the iPhone to 5 October.
According to a senior executive of Swisscom, for obvious reasons we can not mention, the Swiss provider that has previously sold the iPhone 3G and the iPhone 3G, iPhone sales will begin from October 5.

The same source tells us that the iPhone will be launched in September 5th, only to be launched in all states only in October. The manager says 100% sure of the above, because Apple would have already contacted the main mobile operators to agree on how to distribute the iPhone 5.”
Most recent rumors are pointing to same date zone but I think that there is no one can confirm an exact day, anyway let's wait and see.
Source- HERE