iOS 9 Release Date
If you own an old iPhone and you're on the fence about an upgrade to the iPhone 6s, you might want to wait until the iOS 9 update is released. iOS 9 is expected to come with a ton of performance enhancements for older devices including a battery life boost so you might not need to rush into an upgrade.
The iOS release date typically comes two days before the iPhone release date. In this case, the iOS 9 release date should be September 16th for devices like the iPhone 6, iPhond 5s, and so on. Apple will probably confirm at its iPhone event.