Though official invitations have yet to go out, it's all but assured that Apple will unveil the iPhone 5S and iPhone 5C at a special media event on September 10. That said, we're now getting word that U.S.-based carriers are restricting employee vacation time around the September 20 timeframe, which, if history is any indication, suggests that the iPhone will likely launch about 10 days after its unveiling.
Just a few days ago, TMoNews reported that T-Mobile was scheduling employee blackout dates beginning on September 20 and running through September 22. Of course, while that report was admittedly based on an unsubstantiated source, similar reports soon emerged claiming that both AT&T and Verizon were blocking off employee vacation dates during the second half of September.
While there's no way to confirm that the iPhone will launch on September 20, you might want to clear some room off of your own calendars if you're anxious to get your hands on Apple's next-gen smartphone.
Note that the iPhone 5C will likely be Apple's first effort at a low-cost iPhone model and rumor has it the phone will come in a variety of colors, as indicated by the photo above.