Apple doesn’t allow emulators on the App Store for copyright reasons, making it difficult to install third-party emulators and other unapproved applications. The latest upcoming beta version iOS 8.1 patched the famous “Date Trick” that had allowed iOS emulator makers to bypass App Store restrictions and run unofficial emulators. The loophole is currently being used in the wild by the makers of emulators like GBA4iOS and SNES emulator since last year, allowing iOS users to downloaded and installed unapproved apps through the built-in Safari browser.
Source: https://thehackernews.com/2014/10/ios-8-date-trick-loophole-allows-play.html