public static function Obl06($date1, $date2) {
    $t;
    $eps0;

    /* Interval between fundamental date J2000.0 and given date (JC). */
    $t = (($date1 - DJ00) + $date2) / DJC;

    /* Mean obliquity. */
    $eps0 = (84381.406 +
            (-46.836769 +
            ( -0.0001831 +
            ( 0.00200340 +
            ( -0.000000576 +
            ( -0.0000000434) * $t) * $t) * $t) * $t) * $t) * DAS2R;

    return $eps0;
  }