public static function Taiut1($tai1, $tai2, $dta, &$ut11, &$ut12) {
    $dtad;

    /* Result, safeguarding precision. */
    $dtad = $dta / DAYSEC;
    if ($tai1 > $tai2) {
      $ut11 = $tai1;
      $ut12 = $tai2 + $dtad;
    }
    else {
      $ut11 = $tai1 + $dtad;
      $ut12 = $tai2;
    }

    /* Status (always OK). */
    return 0;
  }