function setCookie(c_name,value,expiredays)
{
var exdate=new Date();
exdate.setDate(exdate.getDate()+expiredays);
document.cookie=c_name+ "=" +escape(value)+
((expiredays==null) ? "" : ";expires="+exdate.toGMTString());
}

var now = new Date();
var later = new Date();
// Set time for how long the cookie should be saved
later.setTime(now.getTime() + 365 * 24 * 60 * 60 * 1000);
// Set cookie for the time zone offset in minutes
setCookie("time_zone_offset", now.getTimezoneOffset(), later, "/");
// Create two new dates
var d1 = new Date();
var d2 = new Date();
// Date one is set to January 1st of this year
// Guaranteed to not be in DST
d1.setDate(1);
d1.setMonth(1);
// Date two is set to July 1st of this year
// Guaranteed to be in DST if DST exists for this time zone
d2.setDate(1);
d2.setMonth(7);
// If time zone offsets match, no DST exists for this time zone
if(parseInt(d1.getTimezoneOffset())==parseInt(d2.getTimezoneOffset()))
{
  setCookie("time_zone_dst", "0", 10);
}
// DST exists for this time zone - check if it is currently active
else {
  // Current date is still before or after DST, not containing DST
  if(parseInt(d1.getTimezoneOffset())==parseInt(now.getTimezoneOffset()))
  {
     setCookie("time_zone_dst", "0", 10);
  }
  // DST is active right now with the current date
  else {
    setCookie("time_zone_dst", "1", 10);
  }
}