2
You can change the default date format in the global.php language file. So for english it is in ./language/english/global.php. You'll find 3 defines around line 174-176 (_DATESTRING, _MEDIUMDATESTRING, and _SHORTDATESTRING). You'll see _SHORTDATESTRING is set to 'Y/n/j' - you'll want to change that to 'd/m/Y'. You'll want to make similar changes to the _DATESTRING and _MEDIUMDATESTRING defines.