public static function Taitt($tai1, $tai2, &$tt1, &$tt2) {
    /* TT minus TAI (days). */
    $dtat = TTMTAI / DAYSEC;

    /* Result, safeguarding precision. */
    if ($tai1 > $tai2) {
      $tt1 = $tai1;
      $tt2 = $tai2 + $dtat;
    }
    else {
      $tt1 = $tai1 + $dtat;
      $tt2 = $tai2;
    }

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