Syntax:

<asp:Timer ID="Timer1" runat="server">
</asp:Timer>

Code:

Write these codes on aspx page

 <%-- ScriptManager control manages client script for AJAX enabled ASP.NET pages--%>
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<asp:Timer ID="UpdateTimer" runat="server" Interval="3000" OnTick="UpdateTimer_Tick" />
 <%--OnTick Method Raises the Tick event.--%>
<asp:Label ID="Label1" runat="server" />

Write these code on timer event

protected void UpdateTimer_Tick(object sender, EventArgs e)
{
  Label1.Text = DateTime.Now.ToString();
}

Interval property is set in milisecond.

Run the Project

Page will automatically refresh after 3 second. We can change refresh time using timer control property Interval.