A DateTime does not have a format: it is stored as a a number of microseconds since an arbitrary point in time.
You can use the SQL FORMAT function
] to do it, but I don't recommend it - it is much better to return a DateTime value and then format it for display at the last moment. If you format it in SQL, then you are fixing the format to one which may not be what the user is used to: if he normally gets US format, then European is not helpful. If he expects European and gets Japanese, it is also a pain.