title: Date formatter produces inconsistent results
body: <p>I want to show formatted date instead of timestamp. My code:</p>
  
  <pre><code>private static final String CRAWLER_DATE_FORMAT = "dd-MM-yyyy HH:mm:ss";
  protected static final DateFormat DATE_FORMAT = new SimpleDateFormat(CRAWLER_DATE_FORMAT);
  </code></pre>
  
  <p>This log line is called in every 3 seconds:</p>
  
  <pre><code>LOG.error("Timestamp: " + timestampString + " Formatted Date: " + DATE_FORMAT.format(Long.parseLong(timestampString));
  </code></pre>
  
  <p>My LOG:</p>
  
  <pre><code>Timestamp: 1491078405854 Formatted Date: 16-04-2017 21:25:20 &lt;==
  Timestamp: 1491078405854 Formatted Date: 01-04-2017 23:26:45
  Timestamp: 1491078405854 Formatted Date: 01-04-2017 23:26:45
  Timestamp: 1491078405854 Formatted Date: 01-04-2017 23:26:45
  Timestamp: 1491078405854 Formatted Date: 01-04-2017 23:26:45
  Timestamp: 1491078405854 Formatted Date: 16-04-2017 21:25:20 &lt;==
  Timestamp: 1491078405854 Formatted Date: 01-04-2017 23:26:45
  </code></pre>
  
  <p>Why do I get different results? </p>