The getTimezoneOffset() method returns the difference between the time zones of local time and Greenwich Mean Time (GMT).
This difference is returned as an integer.
Although this is a method of a Date object, the actual date and time associated with the date is irrelevant because the time zone difference is based on the environment settings.
<html>
<head>
<title>Determine Time Zone</title>
</head>
<body>
<script language="JavaScript" type="text/javascript">
<!--
var current_date = new Date();
var current_timezone = current_date.getTimezoneOffset();
document.write("Your time zone is " + current_timezone + " minutes from GMT");
//-->
</script>
</body>
</html>