javaScript DateAdd

    function DateAdd(timeU,byMany,dateObj) {
        var millisecond=1;
        var second=millisecond*1000;
        var minute=second*60;
        var hour=minute*60;
        var day=hour*24;
        var year=day*365;
 
        var newDate;
        var dVal=dateObj.valueOf();
        switch(timeU) {
            case "ms": newDate=new Date(dVal+millisecond*byMany); break;
            case "s": newDate=new Date(dVal+second*byMany); break;
            case "mi": newDate=new Date(dVal+minute*byMany); break;
            case "h": newDate=new Date(dVal+hour*byMany); break;
            case "d": newDate=new Date(dVal+day*byMany); break;
            case "y": newDate=new Date(dVal+year*byMany); break;
        }
        return newDate;
    }