<option value="date" <?php echo $field['save_to'] == 'date' ? 'selected="selected"' : '' ?>>date</option>
<option value="time" <?php echo $field['save_to'] == 'time' ? 'selected="selected"' : '' ?>>time</option>

private function get_date_value() {
$date = $this->simple->get_total_value(Simple::SET_CHECKOUT_CUSTOMER,'date');
        $simple_show_shipping_address = $this->cart->hasShipping() ? $this->config->get('simple_show_shipping_address') : 0;

        if ($simple_show_shipping_address && $this->request->server['REQUEST_METHOD'] == 'POST' && empty($this->request->post['shipping_address_same'])) {
            $date .= ' '.$this->simple->get_total_value(Simple::SET_CHECKOUT_ADDRESS,'date');
        }

        $this->simple->date = $date;
        $this->session->data['date'] = $date;
    }

    private function get_time_value() {
        $time = $this->simple->get_total_value(Simple::SET_CHECKOUT_CUSTOMER,'time');

        $simple_show_shipping_address = $this->cart->hasShipping() ? $this->config->get('simple_show_shipping_address') : 0;

        if ($simple_show_shipping_address && $this->request->server['REQUEST_METHOD'] == 'POST' && empty($this->request->post['shipping_address_same'])) {
            $time .= ' '.$this->simple->get_total_value(Simple::SET_CHECKOUT_ADDRESS,'time');
        }

        $this->simple->time = $time;
        $this->session->data['time'] = $time;
    }

$data['date'] = $this->simple->date;
$data['time'] = $this->simple->time;