Hi
Changed the date on my X1 today with no issues. Follow the manual as it says, but remember it's the 'Set' with the key symbol and not the 'Set' with the date symbol that you’re looking for.
From reading the manual it sounds like this is a setting that's saved on the key fob (along with a few others) and not in the car itself... but I might be wrong.
Anyway, date is now in good old UK format
J.