Using ajax tool kit then work as below code You got timer:

ASPX

<form id="form2" runat="server">

<asp:ScriptManager ID="ScriptManager1" runat="server" />

<asp:Timer runat="server" id="UpdateTimer" interval="1000" ontick="UpdateTimer_Tick" />

<asp:UpdatePanel runat="server" id="TimedPanel" updatemode="Conditional">

<Triggers>

<asp:AsyncPostBackTrigger controlid="UpdateTimer" eventname="Tick" />

</Triggers>

<ContentTemplate>

<asp:Label runat="server" id="DateStampLabel" />

</ContentTemplate>

</asp:UpdatePanel>

</form>

Aspx.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace WebApplication1

{

public partial class _4 : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{


}

protected void UpdateTimer_Tick(object sender, EventArgs e)

{

DateStampLabel.Text = DateTime.Now.ToString();

}

}

}