protected function getNavigationOptions()
 {
     $options = new DataObjectSet();
     $counter = new sfDate($this->start_date->get());
     $counter->subtractMonth(6);
     for ($i = 0; $i < 12; $i++) {
         $options->push(new ArrayData(array('Link' => $this->ShowMonthLink($counter->format('Ym')), 'Selected' => $this->start_date->format('Ym') == $counter->format('Ym') ? 'selected="selected"' : '', 'Month' => CalendarUtil::i18n_date('%B, %Y', $counter->get()))));
         $counter->addMonth();
     }
     unset($counter);
     return $options;
 }