You could create a cookie to use in php. I found this code some where and I use it to get a screen resolution in javascript and set a cookie on the end users machine:
<?
if(isset($_COOKIE["users_resolution"]))
$screen_res = $_COOKIE["users_resolution"];
else //means cookie is not found set it using Javascript
{
?>
<script language="javascript">
<!--
writeCookie();
function writeCookie()
{
var today = new Date();
var the_date = new Date("December 31, 2023");
var the_cookie_date = the_date.toGMTString();
var the_cookie = "users_resolution="+ screen.width +"x"+ screen.height;
var the_cookie = the_cookie + ";expires=" + the_cookie_date;
document.cookie=the_cookie
location = 'index.php';
}
//-->
</script>
<?
}
?>
This should be fairly easy to implement with getTimezoneOffset()
