Sub menus are supported.

ASP.NET WebForms

<daypilot:daypilotmenu id="DayPilotMenu1" runat="server" CssClassPrefix="menu_default" ShowMenuTitle="true">
  <DayPilot:MenuItem Text="Open" Action="JavaScript" JavaScript="edit(e);" ></DayPilot:MenuItem>
  <DayPilot:MenuItem Text="Send" Action="JavaScript" JavaScript="alert('Sending event (id ' + e.value() +')');" ></DayPilot:MenuItem>
  <DayPilot:MenuItem Text="Sub menu" >
      <DayPilot:MenuItem Action="JavaScript" JavaScript="alert('test');" Text="Test" />
  </DayPilot:MenuItem>
</daypilot:daypilotmenu>

JavaScript

var menu = new DayPilot.Menu({items: [
  {text:"Show event ID", onclick: function() {alert("Event value: " + this.source.value());} },
  {text:"Show event text", onclick: function() {alert("Event text: " + this.source.text());} },
  {text:"Show event start", onclick: function() {alert("Event start: " + this.source.start().toStringSortable());} },
  {text:"Go to google.com", href: "http://www.google.com/?q={0}"},
  {text:"CallBack: Delete this event", command: "delete"} ,
          {text:"submenu", items: [
                  {text:"Show event ID", onclick: function() {alert("Event value: " + this.source.value());} },
                  {text:"Show event text", onclick: function() {alert("Event text: " + this.source.text());} }
              ]
          }
],
cssClassPrefix: "menu_default"});