NAV uses date format (and all other formatting setings, too EXCEPT Digit grouping symbol) as set in Control Panel / Regional & Language options. Change the settings thru Control panel as you like.
PS I don`t know why Digit Grouping symbol is an exception - maybe someone knows the reason? It sometimes causes problems with CtrlC-CtrlV to Excel.
Modris, the reason for this is that Windows uses a thousands separator that is not a space, just looks that way.
Replace it in regional settings with a space and your copying will work fine.
(Windows is not using a space to prevent line breaks in the middle of a number in the Office programs.)