Its working fine. Try to copy paste this in separate page;
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="abc" runat="server"></asp:ScriptManager>
<div>
<asp:Timer ID="Timer1" runat="server" OnTick="Timer1_Tick" Interval="2000">
</asp:Timer>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Timer1" EventName="Tick" />
</Triggers>
</asp:UpdatePanel>
</div>
</form>
</body>
C# code on CS file:
protected void Timer1_Tick(object sender, EventArgs e)
{
Label1.Text = DateTime.Now.ToString();
}