How may I schedule when comments can be Opened and Closed?
That should be as simple as:

function MYMODULE_node_view($node, $view_mode, $langcode) {
  if (/* Your logic to determine that comments are closed here */) {
    $node-&gt;content['comments']['#access'] = FALSE;
  }
}


(it'll probably need to be tweaked for your exact requirements, have a look at what else lives in $node-&gt;content['comments'] if you want to hide the form/existing comments separately).