How to load node with AJAX on a Calendar click?
You can take help of Drupal hook_menu with Json object output and a Drupal JS beahvior to handle click event.

Idea : In the click event call an ajax function to your menu callback that gets you a JSON object of required content. Load the content in your desired DOM element.

code for hook_menu; considering your module name 'mymodule'

function mymodule_menu() {
  $items['mymodule/%node/load-content'] = array(
      'page callback' =&gt; 'mymodule_ajax_node_load_content',
      'page arguments' =&gt; array(1),
      'access arguments' =&gt; array('access content'),
  );
  return $items;
}


code for Page callback : 

function mymodule_ajax_node_load_content($node) {
  // The variable holds complete node object for you.

  $data = array();

  $data['body'] = $node-&gt;body['0']['value']; 
  // Consider providing any other node details if required.

  $output = array('status' =&gt; 'ok', 'data' =&gt; $data);

  return drupal_json_output($output);
}


JS code for attaching a behavior to Drupal,

Drupal.behaviors.nodeLinkClick = {
  attach: function(context, settings) {
    // sort by click.
    $("a.node-link").click(function(e){
      e.preventDefault();
      $.ajax({
        url: Drupal.settings.basePath + 'mymodule/' + nid + '/load-content',
        type: 'GET',
        data: data,
        dataType: 'json',
        success: function(response) {
          $(".dom_to_load_content").html(response.data.body);
        },
        error: function() {
          // show error in any DOM.
        },
      });
    });
  }
}


NOTE : The above code not tested; a small snippet cut-out from my project.
Hope this helps you. Let me know if you still facing any problem.