Within Access the only date/time datatype recognized is mm/dd/yyyy hh:nn:ss
It is stored internally as a double. Some input will be assumed. For
instance, unless you enter a year, Access assumes the current year, so you
can enter 5/3 and Access will assume 5/3/2008. An Input Mask can force you
to enter a year or the time or any other part of a date, but it will always
be stored as a double, unless it cannot be resolved. In that case a type
mis-match will occur.
The display is another matter entirely. If you use: mm/dd as the Format
property in a form, you will see 05/03 displayed. Because data entry will
assume the current year, it will still store 05/03/2008.