function y2k(number)    { return (number < 1000) ? number + 1900 : number; }
var today = new Date();
var year = y2k(today.getYear());
var DSTstart = new Date(year,4-1,NthDay(1,1,4,year),2,0,0);
var DSTend   = new Date(year,10-1,NthDay(-1,1,10,year),2,0,0);
function getMS(date) {
    return
Date.UTC(y2k(date.getYear()),date.getMonth(),date.getDate(),date.getHours(),date.getMinutes(),date.getSeconds())
}
var todayMS = getMS(today);
var DSTstartMS = getMS(DSTstart);
var DSTendMS = getMS(DSTend);
if (todayMS > DSTstartMS && todayMS < DSTendMS)
    document.write('Daylight Saving within effect');
else
    document.write('Daylght Saving NOT within effect');