public function enableCalendarDatepicker()
    {
        if (!$this->isEnabledCalendarDatepicker()) {
            // First time enabling
            PageTail::getInstance()
                ->addCssUrl('plugins/datepicker/datepicker.css')
                ->addJsUrl('plugins/datepicker/bootstrap-datepicker.js');

            $this->setDateFormat('yyyy-mm-dd');
        }

        $this->calendar_datepicker_enabled = true;

        return $this;
    }