When any district court in this state shall have entered of record a decree of divorce prior to August 27, 1951, it shall be conclusively presumed that the decree, and all instruments and proceedings in connection therewith, are valid in all respects, notwithstanding some defect or defects as may appear on the face of the record or the absence of any record of such court, unless an action is brought within two years from August 27, 1951, attacking the validity thereof.