SharePoint Add Calendar Overlay Programmatically

This is sample of code to add calendar overlay pro grammatically:

using (SPSite site = new SPSite("http://sp2013-tarek294:8000/"))
{
     using (SPWeb web = site.OpenWeb())
    {
          web.AllowUnsafeUpdates = true;
          SPList list = web.Lists["Calendar"];
          SPView m_view = list.Views["Calendar"];
          m_view.CalendarSettings = SerializeAccessors();
          m_view.Update();
          web.AllowUnsafeUpdates = false;

    }
}

private static string SerializeAccessors()
{
 return "<AggregationCalendars>
  <AggregationCalendar Id="{56594c0c-5649-458e-a4e3-939589ddc75d}" Type="SharePoint" Name="Holiday" Description="Holiday" Color="5" AlwaysShow="True" CalendarUrl="/Lists/Calendar/Holiday.aspx">
    <Settings WebUrl="http://sp2013-tarek294:8000" ListId="{6913f374-1a4e-4772-8c5f-9f5d56610f71}" ViewId="{0091da5e-e5a4-4e1f-ab96-19f96eeb59fa}" ListFormUrl="/Lists/Calendar/DispForm.aspx" />
  </AggregationCalendar>
  <AggregationCalendar Id="{d65114d1-cb97-41db-a7eb-7cc3614c957e}" Type="SharePoint" Name="Meeting" Description="Meeting" Color="8" AlwaysShow="True" CalendarUrl="/Lists/Calendar/Meeting.aspx">
    <Settings WebUrl="http://sp2013-tarek294:8000" ListId="{6913f374-1a4e-4772-8c5f-9f5d56610f71}" ViewId="{68513c26-b132-4d9e-b9ca-acc74a4cf1dc}" ListFormUrl="/Lists/Calendar/DispForm.aspx" />
  </AggregationCalendar>
  -->
  <AggregationCalendar Id="{cd33c105-6dd4-4cb9-b6ee-ca26dfcdb70e}" Type="SharePoint" Name="TestView" Description="TestView" Color="3" AlwaysShow="True" CalendarUrl="/Lists/Calendar/TestView.aspx">
    <Settings WebUrl="http://sp2013-tarek294:8000" ListId="{6913f374-1a4e-4772-8c5f-9f5d56610f71}" ViewId="{2D81DDC1-A360-4585-BF4A-7C0E512C7AA8}" ListFormUrl="/Lists/Calendar/DispForm.aspx" />
  </AggregationCalendar>
</AggregationCalendars>"
}

SharePoint 2013 Read Overlay setting using javascript

You can use the following the code to retrieve Calendar Overlay settings using Javascript:

EnsureScriptFunc('sp.js', 'SP.ClientContext', function(){

            var clientContext = new SP.ClientContext.get_current();

            if (clientContext != undefined && clientContext != null) {

                 var web = clientContext.get_web();

                                                                                                                               

                 var listCollection = web.get_lists();

                 var list = listCollection.getByTitle("Calendar");

                 var viewCollection = list.get_views();

                 this.view = viewCollection.getByTitle("Calendar");

                 clientContext.load(this.view);

                 clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceeded),    Function.createDelegate(this, this.onQueryFailed));

}

});

 function onQuerySucceeded() {

        alert(this.view.get_htmlSchemaXml()); //this contains overlays settings

 }

                               

 function onQueryFailed(sender, args) {

       alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());

 }