JS年月日级联得不到值

function initDate(year, month, day) {
            //每个月的初始天数
            MonDays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
            //当前的年份
            var y = new Date().getFullYear();
            //当前的月份
            var m = new Date().getMonth() + 1; //javascript月份为0-11
            //但前的天份
            var d = new Date().getDate();
            //以今年为准，向后2年，填充年份下拉框
            for (var i = y - 10; i < (y + 20); i++) {
                year.options.add(new Option(i, i));
            }
            //选中今年
            year.value = y;
            //填充月份下拉框
            month.options.add(new Option(1, 1));
            month.options.add(new Option(2, 2));
            month.options.add(new Option(3, 3));
            month.options.add(new Option(4, 4));
            month.options.add(new Option(5, 5));
            month.options.add(new Option(6, 6));
            month.options.add(new Option(7, 7));
            month.options.add(new Option(8, 8));
            month.options.add(new Option(9, 9));
            month.options.add(new Option(10, 10));
            month.options.add(new Option(11, 11));
            month.options.add(new Option(12, 12));
            //选中当月
            month.value = m;            //获得当月的初始化天数
            var n = MonDays[m - 1];
            //如果为2月，天数加1
            if (m == 2 && isLeapYear(year.options[year.selectedIndex].value))
                n++;
            //填充日期下拉框
            createDay(n, day);
            //选中当日
            day.value = new Date().getDate();
        }
        function change(year, month, day) //年月变化，改变日
        {
            var y = year.options[year.selectedIndex].value;
            var m = month.options[month.selectedIndex].value;
            //if (m == "" ){  clearOptions(day); return;}
            var n = MonDays[m - 1];
            if (m == 2 && isLeapYear(y)) {
                n++;
            }
            createDay(n, day)        }
        function getResult(year, month, day, res) {
            var y = year.options[year.selectedIndex].value;
            var m = month.options[month.selectedIndex].value;
            var d = day.options[day.selectedIndex].value;
            
            res.innerHTML = y +"-"+ m+"-"+ d;
        }
        function createDay(n, day) //填充日期下拉框
        {
            //清空下拉框
            clearOptions(day);
            //几天，就写入几项
            day.options.add(new Option(01, 01));
            day.options.add(new Option(02, 02));
            day.options.add(new Option(03, 03));
            day.options.add(new Option(04, 04));
            day.options.add(new Option(05, 05));
            day.options.add(new Option(06, 06));
            day.options.add(new Option(07, 07));
            day.options.add(new Option(08, 08));
            day.options.add(new Option(09, 09));
            for (var i = 10; i <= n; i++) {
                day.options.add(new Option(i, i));
            }
        }        function clearOptions(ctl)//删除下拉框中的所有选项
        {
            for (var i = ctl.options.length - 1; i >= 0; i--) {
                ctl.remove(i);
            }
        }
        function isLeapYear(year)//判断是否闰年
        {
            return (year % 4 == 0 || (year % 100 == 0 && year % 400 == 0));
        }
        //-->
    </script>上面是JS代码
下面是级联控件
 <select runat="server" id="year44" name="select_year" onchange="change(this, document.getElementById('month44'), document.getElementById('day44'));getResult(this, document.getElementById('month44'), document.getElementById('day44'),document.getElementById('Time44'))"></select>年
                                        <select runat="server" id="month44" name="select_month" onchange="change(document.getElementById('year44'), this,document.getElementById('day44'));getResult(document.getElementById('year44'), this,document.getElementById('day44'),document.getElementById('Time44'))"></select>月 
                                        <select name="select_day" runat="server" id="day44" onchange="getResult(document.getElementById('year44'),document.getElementById('month44'),this,document.getElementById('Time44'))"></select>日
我在后台通过
model.Colum44n = LTP.Common.StringClass.EncodeString(Time42.Text.Trim());
string a = year44.Value + month44.Value + day44.Value;
都不能得到下来狂的值