iOS apps in Xcode have a "Base SDK" (which is the actual SDK you're building against: must be iOS 7.0 from Feb 1). But you then also set a "deployment target", which is effectively the oldest version of iOS you still want to support. Set this to iOS 6, for example, and you'll be supporting both versions, even after Feb 1.

One of course needs to be careful about using new APIs/features in this situation (detect whether a certain method/selector exists before using it, for instance) – as we don't want to throw runtime errors on the older OS.

http://stackoverflow.com/questions/1358033/iphone-base-versu...

http://stackoverflow.com/questions/986589/how-do-you-optiona...