The DateTime attribute setting 'Localize' takes care of a front-end problem and therefor has no place in the Domain model. It should not be there at all. It should be part of the DateTime element at the front-end.
Setting it to 'No' is advised by the Mendix documentation for cases where you are not interested in the time at all (like a date of birth). If that is the only reason, and there does not appear to be another one, than the correct option would be to have an attribute-type 'Date' which only stores a date.
Also adding an attribute type 'Time' is only logic.