That won't "convert" the dates, just display them differently.

The underlying value will still be 09/20/08 or September 20, 2008

Do you need them actually "converted" to a text value of 080920 ?

="0"&(YEAR(A1)-2000)*10000+MONTH(A1)*100+DAY(A1)

Or even like this..

=TEXT(A1,"yymmdd")

Rick