public static function Pr00($date1, $date2, &$dpsipr, &$depspr) {
    $t;

    /* Precession and obliquity corrections (radians per century) */
    $PRECOR = -0.29965 * DAS2R;
    $OBLCOR = -0.02524 * DAS2R;

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

    /* Precession rate contributions with respect to IAU 1976/80. */
    $dpsipr = $PRECOR * $t;
    $depspr = $OBLCOR * $t;

    return;
  }