I read a thread that said this was addressed in FileMaker 15 for number formatting, but I see the problem with date formatting. When a date field is formatted as a pop-up menu, the date always appears in MM/DD/YYYY format. On the left is the pop-up version, and on the right is the Edit Box version. This is on a UK system with a file that was originally created in the UK.
I ran into something like this recently. It made me angry and in the end I needed to force the date arrangement with a calculation because it was a quick solution to the problem, but not desirable. This was also on a file originally created in the UK.