Custom format date cells-Autofilter doesn't work right
 

I have created a custom format for my cells (mmm dd). The autofilter works
correctly (June 1 then Aug 1).
When I format the cells as (mmm dd yy), the autofilter doesn't seem to
recognize it the same (Aug 1 07 shows before June 1 07).
The formats used to be fine without the year, but I need it now.
I want my autofilter to show in calendar sequence, not alphabetically or
numerically.
Any ideas?
Thanks,
Joe
Excel 2003