diff -rupN fullcalendar.old/fullcalendar_options/fullcalendar_options.module fullcalendar.new/fullcalendar_options/fullcalendar_options.module
--- a/fullcalendar_options/fullcalendar_options.module	2013-12-09 14:02:15.000000000 +0800
+++ b/fullcalendar_options/fullcalendar_options.module	2014-07-31 17:15:20.569624614 +0800
@@ -177,3 +177,13 @@ if (module_exists('colorbox') && !functi
     return fullcalendar_options_fullcalendar_api();
   }
 }
+
+
+/**
+ * Add Overlay integration.
+ */
+if (module_exists('overlay') && !function_exists('overlay_fullcalendar_api')) {
+  function overlay_fullcalendar_api() {
+    return fullcalendar_options_fullcalendar_api();
+  }
+}
diff -rupN fullcalendar.old/fullcalendar_options/includes/overlay.fullcalendar.inc fullcalendar.new/fullcalendar_options/includes/overlay.fullcalendar.inc
--- a/fullcalendar_options/includes/overlay.fullcalendar.inc	1970-01-01 08:00:00.000000000 +0800
+++ b/fullcalendar_options/includes/overlay.fullcalendar.inc	2014-07-31 17:18:36.445629392 +0800
@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * @file
+ * Provides extra FullCalendar configuration options for Overlay.
+ */
+
+/**
+ * Implements hook_fullcalendar_options_info().
+ */
+function overlay_fullcalendar_options_info() {
+  return array(
+    'overlay' => array(
+      'name' => t('Overlay'),
+      'js' => TRUE,
+      'parent' => 'fullcalendar_options',
+    ),
+  );
+}
+
+/**
+ * Implements hook_fullcalendar_options_definition().
+ */
+function overlay_fullcalendar_options_definition() {
+  $options['overlay']['contains'] = array(
+    'overlay' => array(
+      'default' => FALSE,
+      'bool' => TRUE,
+    ),
+  );
+  return $options;
+}
+
+/**
+ * Implements hook_fullcalendar_options_form().
+ */
+function overlay_fullcalendar_options_form(&$form, &$form_state, &$view) {
+  $form['overlay']['overlay'] = array(
+    '#type' => 'checkbox',
+    '#title' => t('Open events with Overlay'),
+    '#default_value' => $view->options['overlay']['overlay'],
+    '#data_type' => 'bool',
+  );
+
+  $form['sameWindow']['#dependency'] = array('edit-style-options-overlay-overlay' => array(0));
+}
+
+/**
+ * Implements hook_fullcalendar_options_process().
+ */
+function overlay_fullcalendar_options_process(&$variables, &$settings) {
+  if (empty($settings['overlay']['overlay'])) {
+    unset($settings['overlay']);
+  }
+}
diff -rupN fullcalendar.old/fullcalendar_options/js/overlay.fullcalendar.js fullcalendar.new/fullcalendar_options/js/overlay.fullcalendar.js
--- a/fullcalendar_options/js/overlay.fullcalendar.js	1970-01-01 08:00:00.000000000 +0800
+++ b/fullcalendar_options/js/overlay.fullcalendar.js	2014-07-31 17:08:59.009615306 +0800
@@ -0,0 +1,26 @@
+(function($) {
+Drupal.fullcalendar.plugins.overlay = {
+  options: function (fullcalendar, settings) {
+    if (!settings.overlay) {
+      return;
+    }
+    settings = settings.overlay;
+
+    var options = {
+      eventClick: function(calEvent, jsEvent, view) {
+        // Use overlay only for events based on entities
+        if (calEvent.eid !== undefined) {
+          var url = calEvent.url;
+          url = '#overlay=' + url;
+          $.overlay({
+            href: url
+          });
+        }
+        return false;
+      }
+    };
+    return options;
+  }
+};
+
+}(jQuery));
diff -rupN fullcalendar.old/sites/all/modules/fullcalendar/fullcalendar_options/includes/overlay.fullcalendar.inc fullcalendar.new/sites/all/modules/fullcalendar/fullcalendar_options/includes/overlay.fullcalendar.inc
--- a/fullcalendar_options/includes/overlay.fullcalendar.inc	1970-01-01 08:00:00.000000000 +0800
+++ b/fullcalendar_options/includes/overlay.fullcalendar.inc	2014-07-31 17:06:02.501611001 +0800
@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * @file
+ * Provides extra FullCalendar configuration options for Overlay.
+ */
+
+/**
+ * Implements hook_fullcalendar_options_info().
+ */
+function overlay_fullcalendar_options_info() {
+  return array(
+    'overlay' => array(
+      'name' => t('Overlay'),
+      'js' => TRUE,
+      'parent' => 'fullcalendar_options',
+    ),
+  );
+}
+
+/**
+ * Implements hook_fullcalendar_options_definition().
+ */
+function overlay_fullcalendar_options_definition() {
+  $options['overlay']['contains'] = array(
+    'overlay' => array(
+      'default' => FALSE,
+      'bool' => TRUE,
+    ),
+  );
+  return $options;
+}
+
+/**
+ * Implements hook_fullcalendar_options_form().
+ */
+function overlay_fullcalendar_options_form(&$form, &$form_state, &$view) {
+  $form['overlay']['overlay'] = array(
+    '#type' => 'checkbox',
+    '#title' => t('Open events with Overlay'),
+    '#default_value' => $view->options['overlay']['overlay'],
+    '#data_type' => 'bool',
+  );
+
+  $form['sameWindow']['#dependency'] = array('edit-style-options-overlay-overlay' => array(0));
+}
+
+/**
+ * Implements hook_fullcalendar_options_process().
+ */
+function overlay_fullcalendar_options_process(&$variables, &$settings) {
+  if (empty($settings['overlay']['overlay'])) {
+    unset($settings['overlay']);
+  }
+}