title: Convert date formatter to another date formatter
body: <p>I have a date in string like this: <code>10/07/2016</code></p>
  
  <p>I want to convert like this: <code>10 July 2016</code></p>
  
  <p>I do like this:</p>
  
  <pre><code>struct NSDateFormatterType {
      static let API_FORMAT = "dd/mm/yyyy"
      static let DISPLAY_FORMAT = "dd MMMM yyyy"
  }
  
  extension NSDate {
    class func convertDateDisplayFormat(dateString: String) -&gt; String {
      let dateFormatter = NSDateFormatter()
      dateFormatter.dateFormat = NSDateFormatterType.API_FORMAT
      if let date = dateFormatter.dateFromString(dateString) {
          dateFormatter.dateFormat = NSDateFormatterType.DISPLAY_FORMAT
          return dateFormatter.stringFromDate(date)
      } else {
          return dateString
      }
  }
  </code></pre>
  
  <p>But it gives me: <code>10 January 2016</code></p>
  
  <p>What I do wrong here?</p>