public function timed_discussion_tooltip($discussion, $visiblenow) {
        $dates = array();
        if ($discussion->timestart) {
            $dates[] = get_string('displaystart', 'mod_forum').': '.userdate($discussion->timestart);
        }
        if ($discussion->timeend) {
            $dates[] = get_string('displayend', 'mod_forum').': '.userdate($discussion->timeend);
        }

        $str = $visiblenow ? 'timedvisible' : 'timedhidden';
        $dates[] = get_string($str, 'mod_forum');

        $tooltip = implode("\n", $dates);
        return $this->pix_icon('i/calendar', $tooltip, 'moodle', array('class' => 'smallicon timedpost'));
    }