In a few weeks I'll be releasing my iOS app to a group of beta testers. I'm allowing them to test from a Friday evening until the following Sunday night. I want to disallow any usage after that Sunday. I don't want to use
NSDate because testers could change the date on their device and keep playing after the session ended. Any ideas?
The date option is probably good enough as most people won't bother changing the date on their device, it would mess up too many other apps. The only case to worry about there would be someone with a device dedicated to your game.
Another option though: add a network request to your server with some code that says if it's allowed to play or not, then you can just change the flag on your server.