Helper Class - TEC Recurring Event Concatenation

/**
 * This is a short helper class that can be used to "concatenate"
 * events so that the dates of future recurring instances are listed
 * beside the main event.
 */
class EventListOrganiser {
    protected static $alreadyLooped = array();
    protected static $query;


    public static function hasDisplayedAlready() {
        $displayed = in_array(get_the_ID(), self::$alreadyLooped);
        self::$alreadyLooped[] = get_the_ID();
        return $displayed;
    }


    public static function listFutureRecurringEventDates() {
        self::findRecurringPosts(get_the_ID(), array(__CLASS__, 'printDates'));
    }


    protected function findRecurringPosts($id, $callback) {
        self::$query = new WP_Query($GLOBALS['wp_query']->query_vars);
        $idList = array();

        while (self::$query->have_posts()) {
            self::$query->the_post();

            if (self::$query->post->ID === $id) {
                if (in_array($id, $idList))
                    call_user_func($callback);

                $idList[] = $id;
            }
        }
    }


    protected function printDates() {
        echo '<li>'.tribe_get_start_date().'</li>';
    }
}