title: Storing a timestamp value and showing it to the UI
body: <p>in my application I get, using JSON, a timestamp value like this :</p>
  
  <ul>
  <li>1278321016000 for 2010-07-05 11:10:16.0 CEST</li>
  <li>1278436867000 for 2010-07-06 19:21:07.0 CEST</li>
  </ul>
  
  <p>I'm currently storing this value to long type, but I wonder if it is the right way, have I to search thing with NSTimeInterval ?</p>
  
  <p>What would be, after storing this value, the best way to show this in a UILabel object, looking like "YYYY-MM-DD hh:mm:ss" ?</p>
  
  <p>I tried to use NSDate object, but I can't get the initWithTimeIntervalSince1970 method...</p>
  
  <p>Thank you in advance !</p>