title: Invalid date when submitting Google XML sitemap
body: <p>When validating my <a href="http://www.moto-trek.co.uk/sitemap/xml" rel="noreferrer">XML sitemap</a>, google says:</p>
  
  <p><em>Invalid date
  An invalid date was found. Please fix the date or formatting before resubmitting.</em></p>
  
  <p>I convert the mysql timestamp by:</p>
  
  <pre><code>gmdate('Y-m-d\TH:i:s', strtotime($row['modified']['value']))
  </code></pre>