clone your file with a not American FM version.
its not an FMP thing.. FMP grabs the date from ur system...
so, assuming you are using windows XP (possibly the same in VISTA)
go to control panels / regional and language options / click on 'customize' / click on the 'date' tab /
then in the 'short date format' section, select the dd/mm/yy option in the drop down menu
click ok, then click ok again...
close FMP and reopen it, and ur dates should have the format dd-mm-yy
if u're using a mac, i got no idea how to change the settings, but im sure u will figure it out..