NOT TESTED!

date_correction.sql

DECLARE
  FUNCTION date_if_possible(v1 IN VARCHAR2)
    RETURN DATE AS
	dte_corrected DATE;
	BEGIN
	  dte_corrected = to_date(
                            to_char(to_number(regexp_substr(v1,'[^,]+', 15, 1)) - 100) || 
                            lpad(to_char(to_number(regexp_substr(v1,'[^,]+', 15, 2)) - 100),2,'0') ||
                            lpad(regexp_substr(v1,'[^,]+', 15, 3),2,'0') ||
                            lpad(regexp_substr(v1,'[^,]+', 15, 4),2,'0'),
                            'YYYYMMDD');
	  RETURN dte_corrected;
	EXCEPTION
	  RETURN null;
	END
BEGIN
  UPDATE me.occasionally_corrupt_table a
     SET a.dte_time_period = date_if_possible(dump(a.dte_time_period))
   WHERE to_char(a.dte_time_period,'YYYYMMDD') = '00000000'
     AND date_if_possible(dump(a.dte_time_period)) IS NOT NULL;
END

would totally date