title: iOS how to detect user has changed system time, and if not compare device time with server time
body: <p>The requirement is that have to detect if the system time of iPhone is changed by user manually. For that I have used     </p>
  
  <pre><code>NSNotificationCenter.defaultCenter().addObserver(self, selector: "timeChangedNotification:", name: NSSystemClockDidChangeNotification, object: nil)
  </code></pre>
  
  <p>and</p>
  
  <pre><code> func timeChangedNotification(notification:NSNotification){
      println("Device time has been changed...")
      }
  </code></pre>
  
  <p>But not getting the results.
  Also if this time is not changed means it is automatic time provided by network then have to compare with server time.How can this be done? Please give help for the same.</p>