Two ways:
The obvious one:
SELECT CAST(CAST(20000000+your_date AS CHAR(8)) AS DATE FORMAT 'YYYYMMDD');
F.Ex.:
SELECT CAST(CAST(20000000+100221 AS CHAR(8)) AS DATE FORMAT 'YYYYMMDD');
*** Query completed. One row found. One column returned.
*** Total elapsed time was 1 second.
(20000000+100221)
-----------------
20100221
The cool one:
SELECT CAST(1000000+your_date AS DATE);
F.Ex.:
SELECT CAST(1000000+100221 AS DATE);
*** Query completed. One row found. One column returned.
*** Total elapsed time was 1 second.
(1000000+100221)
----------------
2010-02-21
HTH.
Cheers.
Carlos.