Apple will reportedly release its new iPhone 5S and iPhone 5C on September 20th for retail in US. This date also matches with T-Mobile's reported employee blackout date schedule between September 20th and 22nd.
Apple is said to announce its new iPhone line-up on September 10th. However, its launch date in US is widely speculated to be September 20th. What is new now? A recent report by TmoNews supports this launch date. It is reported that T-Mobile is planning employee blackout date schedule in between September 20th and 22nd for new iPhone release. These dates support the previously rumored September 20th iPhone launch date.
It means that Apple's new iPhone 5S and iPhone 5C can hit stores on September 20th. Carriers schedule many dates for blackout first. But as the product release date approaches near, retailers shortened their date list. But other carrier networks like AT&T and Verizon have different plans for blackout dates. So we cannot be sure until some official announcement come on scene.