Sorry if this is doubled we lost power when I hit send and I don't see it

I have a pivot chart where the x axis has dates. It currently is displayed
as 7/31/08 and I need it to be Jul-08. I have gone into the format area
chosen number then date and chosen the Jul-08 format but it doesn't change on
the Pivot chart. it still shows as 7/31/08. How can I change this I think
I'm choosing the right thing but since it hasn't changed I guess I'm not
HELP!!!!!!
--
Cher