Calling WebMethod From Javascript

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

 <script language="javascript">
 function UpdateTime() {
   PageMethods.GetCurrentDates(OnSucceeded, OnFailed); 
 }
 
 function OnSucceeded(result, userContext, methodName) {
   $get('lbldate').innerHTML = result; 
 }
 
 function OnFailed(error, userContext, methodName) {
   $get('lbldate').innerHTML = "An error occured.";
 }
script>
<asp:Label runat="server" ID="lbldate" Text="Update Me!" /><br />
<input type="button" id="Button2" value="Web Method Update" 
  onclick="UpdateTime();" />

[WebMethod]
public static string GetCurrentDate()
{
  return DateTime.Now.ToLongDateString();
}