<script src="js/jquery-3.3.1.js" type="text/javascript"></script>
<link href="css/jquery-ui.css" rel="stylesheet" type="text/css" />
<link href="css/bootstrap.min.css" rel="stylesheet" type="text/css" />
<link href="css/bootstrap-timepicker.min.css" rel="stylesheet" type="text/css" />
<script src="js/jquery-ui.js" type="text/javascript"></script>
<script src="js/bootstrap.min.js" type="text/javascript"></script>
<script src="js/bootstrap-timepicker.min.js" type="text/javascript"></script>

<script>
            $(".timepicker").timepicker
</script>

<asp:TextBox ID="StartTime" data-provide="timepicker" CssClass="timepicker" runat="server" />