title: DateFormatter return nil in some case
body: <p>I have two date string <strong>str1</strong> &amp; <strong>str2</strong>. When I get date from <strong>str1</strong>, it works well. But with <strong>str2</strong>, it returns nil. I can't understand why.</p>
  
  <pre><code>let dateFormatter = DateFormatter()
  dateFormatter.dateFormat = "yyyy-MM-dd'T'hh:mm:ss.SSSZ"
  
  let str1 = "2019-04-11T12:01:43.694406Z"
  let str2 = "2019-04-16T17:00:16.124653Z"
  
  let date = dateFormatter.date(from: str1)
  
  if let date = date {
      let formatter = DateFormatter()
      formatter.dateFormat = "yyyy-MM-dd"
      let result = formatter.string(from: date)
  
      return result
  }
  </code></pre>