title: Swift - extracting hours from NSDate, parsing string issue
body: <p>I receive a string in Json and first of all I have to do is to convert it into NSDate. The problem is, none of string formats I used is valid. the code goes as follows:</p>
  
  <pre><code>let formatter = NSDateFormatter()
  formatter.dateFormat = "yyyy-MM-dd hh:mm:ss"
  var output = formatter.dateFromString("2000-01-01T00:00:00.000Z")
  let timeString = formatter.stringFromDate(output)
  </code></pre>
  
  <p>as far as I know, if I want to retrieve hours from NSData, I have to call formatter once more </p>
  
  <pre><code>formatter.dateFormat = "hh"
  </code></pre>
  
  <p>and call it on NSDate obtained from string. Am I right?
  My first question is: how to make the determine proper date format so the output will not be evaluated to nil? The second question is: Do I get it right or there is a simpler method or generally way to retrieve the hours from the following string: "2000-01-01T00:00:00.000Z" ? I know I can do it via dealing with mere string without involving dateFormatter and NSDate, but won't such solution be vulnerable? Please advice me what's the simplest(and robust) way to deal with this.</p>
  
  <p>Thanks in advance</p>