Validate Event Date

Hi,
I've just added a couple of lines of code in order to verify that the event has valid dates (in the original version you can enter 35 January and it gets transformed to 4 of February).

This is the reworked event_validate_form_date

/**
 * Validates the start and end times in a node form submission.
 * - Changes 24 hour time to 12 hour time (if the module is configured to do this).
 *  - Adjusts times for time zone offsets.
 *
 * @ingroup event_support
 * @param $node The submitted node with form data.
 * @param $date The name of the event's date ('start' or 'end') to validate and set.
 */
function event_validate_form_date(&$node, $date) {
  $prefix = $date .'_';
  /**
   *  If using javascript pop-up calendar, convert input date back to individual date parts expected by the validator
   */
  if (module_exists('jscalendar')) {
    $get = $prefix . 'date';
    $this_date = $node->$get;
    $timestamp = mktime(substr($this_date, 11, 2), substr($this_date, 14, 2), substr($this_date, 17, 2), substr($this_date, 5, 2), substr($this_date, 8, 2), substr($this_date, 0, 4));
    $node->{$prefix . 'year'} = date('Y', $timestamp);
    $node->{$prefix . 'month'} = date('n', $timestamp);
    $node->{$prefix . 'day'} = date('d', $timestamp);
    $node->{$prefix . 'hour'} = variable_get('event_ampm', '0') ? date('H', $timestamp) : date('g', $timestamp);
    $node->{$prefix . 'minute'} = date('i', $timestamp);
  }

  // If we have all the parameters, re-calculate $node->event_$date .
  if (isset($node->{$prefix . 'year'}) && isset($node->{$prefix . 'month'}) && isset($node->{$prefix . 'day'}) && isset($node->{$prefix . 'hour'}) && isset($node->{$prefix . 'minute'})) {
    $hour = $node->{$prefix . 'hour'};
    if (variable_get('event_ampm', '0')) {
      if (($node->{$prefix . 'ampm'} == 'pm') && ($hour != 12)) {
        $hour += 12;
      }
      elseif (($node->{$prefix . 'ampm'} == 'am') && ($hour == 12)) {
        $hour -= 12;
      }
    }
    if (!checkdate($node->{$prefix . 'month'},$node->{$prefix . 'day'},$node->{$prefix . 'year'}))
    {
    	form_set_error($prefix.'date', t($prefix.'date is invalid, please check.'));
    }

    // translate the input values to GMT and set the node property value
    $offset = event_get_offset($node->timezone, gmmktime($hour, $node->{$prefix . 'minute'}, 0, $node->{$prefix . 'month'}, $node->{$prefix . 'day'}, $node->{$prefix . 'year'}));
    $node->{'event_'. $date} = _event_mktime($hour, $node->{$prefix . 'minute'}, 0, $node->{$prefix . 'month'}, $node->{$prefix . 'day'}, $node->{$prefix . 'year'}, $offset);
  }
  elseif (!$node->$date) {
    // Round to nearest hour:
    $now = _event_user_time();
    $node->$date = $now - ($now % (60 * 60));
  }
}