&gt; Most webservers fill this date field with zeros, about 10% use the actual date, including the timezone<p>They can&#x27;t include the timezone since the field is a unix timestamp, there&#x27;s no room for the timezone.<p>Apparently the script just assumes whichever date is stored in the mtime field is a local date (when the spec suggests UTC&#x2F;GMT): <a href="https:&#x2F;&#x2F;github.com&#x2F;jcarlosn&#x2F;gzip-http-time&#x2F;blob&#x2F;master&#x2F;time.php#L29" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;jcarlosn&#x2F;gzip-http-time&#x2F;blob&#x2F;master&#x2F;time....</a>