The field birthdate for a Customer is set to type “Date”, but when I export it, it contains an entry in a DateTime format, e.g. “28/04/2017 01:00:00” (which is then also the expected input format for file upload).
The Date format in Locale settings is set to “2013-10-23”
I don’t know much about DateTime fields in PHP, but since nobody else is answering you, I can only comment that it’s normal in many languages to have only one base type allowing for time and date, and then just treat them differently when displaying to the users.
So, the real question is this: do you have any practical problems with getting a TimeDate in the export? Can’t you just ignore the time?