title: I get nil when using NSDateFormatter in swift
body: <p>This is my code :</p>
  
  <pre><code>println(myStringDate)    // 2015-02-26T17:46:34.000Z
  let dateFormatter = NSDateFormatter()
  dateFormatter.dateFormat = "YYYY-MM-DDTHH:mm:ss.sssZ"
  let myDate = dateFormatter.dateFromString(myStringDate)
  println(myDate)        // nil
  </code></pre>
  
  <p>Why nil ? What am I doing wrong ?</p>