How to get DOB value created by javascript using C#?

Hi,
I create 3 drop down lists to store year, month and day but now I don't know how to store them into database.
As I create the date value with javascript, and now I unable to retrieve the value.Can somebody help me?

Javascript :

Code:

 <script type="text/javascript">
        var month = new Array(11);
        month[0] = "Jan";
        month[1] = "Feb";
        month[2] = "Mar";
        month[3] = "Apr";
        month[4] = "May";
        month[5] = "Jun";
        month[6] = "Jul";
        month[7] = "Aug";
        month[8] = "Sep";
        month[9] = "Oct";
        month[10] = "Nov";
        month[11] = "Dec";
        var date = new Date();
        function getYear() {
            var opt = new Option("Year", "Year");
            document.forms[0]["ddlBirthDateYear"].options.add(opt);
            var currentyear = 2012;            
            var i = 0;           
            for (i = 1977; i < currentyear - 3; i++) {
                var item = new Option(i, i);
                document.forms[0]["ddlBirthDateYear"].options.add(item);
            }
        }
        function getMonth() {
            var opt = new Option("Month", "Month");
            document.forms[0]["ddlBirthDateMonth"].options.add(opt);
            for (var i = 0; i <= 11; i++) {
                var item = new Option(month[i], month[i]);
                document.forms[0]["ddlBirthDateMonth"].options.add(item);
            }
        }
        function getDays() {
            //to clear all the items from ddDay drop down list simply set the length property to 0.
            document.forms[0]["ddlBirthDateDay"].length = 0;            
            if (document.forms[0]["ddlBirthDateYear"].selectedIndex > 0 && document.forms[0]["ddlBirthDateMonth"].selectedIndex > 0) {
                var yy = document.forms[0]["ddlBirthDateYear"].value;
                var mm = document.forms[0]["ddlBirthDateMonth"].selectedIndex;
                // alert(yy + "\n" + mm);
                switch (mm) {
                    case 1:
                    case 3:
                    case 5:
                    case 7:
                    case 8:
                    case 10:
                    case 12:
                        for (var i = 1; i <= 31; i++) {
                            var item = new Option(i, i);
                            document.forms[0]["ddlBirthDateDay"].options.add(item);
                        }
                        break;
                    case 4:
                    case 6:
                    case 9:
                    case 11:
                        for (var i = 1; i <= 30; i++) {
                            var item = new Option(i, i);
                            document.forms[0]["ddlBirthDateDay"].options.add(item);
                        }
                        break;
                    case 2:
                        //to calculate if the year is a leap year or not.
                        if (yy % 4 == 0) {
                            for (var i = 1; i <= 29; i++) {
                                var item = new Option(i, i);
                                document.forms[0]["ddlBirthDateDay"].options.add(item);
                            }
                        }
                        else {
                            for (var i = 1; i <= 28; i++) {
                                var item = new Option(i, i);
                                document.forms[0]["ddlBirthDateDay"].options.add(item);
                            }
                        }
                }
            }
        }
    </script>

HTML :

Code:

  <div style="float: right; padding-right: 70%;" >                    
                        <asp:DropDownList ID="ddlBirthDateYear" runat="server">       
                        </asp:DropDownList>  
                        &nbsp;
                        <asp:DropDownList ID="ddlBirthDateMonth" runat="server" onChange="getDays()">
                        </asp:DropDownList>
                        &nbsp;
                        <asp:DropDownList ID="ddlBirthDateDay" runat="server">
                            <asp:ListItem Value="Day"></asp:ListItem>
                        </asp:DropDownList>
                    </div>