I've recently come across KPlato and it looks like it could be a really useful tool for me except for one thing: all the dates are in American. This is really confusing as I never use American dates system. Is there any way to change it?

I've tried changing 'Country/Region & Language' which remains changed and changes the money in KPlato, but the date format will not change.

Any help would be greatly appreciated, thanks!

Have you checked to see if KPlato has it's own settings for this? KPlato should ideally follow the KDE wide date format...