function SetCookie(cookieName, cookieValue, nDays)
{
    var today = new Date();
    var expire = new Date();
    
    if (nDays==null || nDays==0)
        nDays=1;
        
    expire.setTime(today.getTime() + 3600000 * 24 * nDays);
    document.cookie = cookieName+"="+escape(cookieValue) + ";expires="+expire.toGMTString();
}

var d = new Date();
var utcOffset = d.getTimezoneOffset() / 60;
SetCookie("UTCOffset", -utcOffset, 30);