How to determine the date an app is installed or used for the first time?

Question

I\'m planning on opening up an in app store and I\'d like to give existing users some of the items for free.

I thought of releasing an update which would store some

Answer 1

Swift solution:

let urlToDocumentsFolder = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).last!
//installDate is NSDate of install
let installDate = (try! NSFileManager.defaultManager().attributesOfItemAtPath(urlToDocumentsFolder.path!)[NSFileCreationDate])
print("This app was installed by the user on \(installDate)")