Every form field can have two different values associated with it: The actual data, and the display value (or the formatted value). I assume that you've created this field so that the data value entered gets formatted as mm/dd/yyyy, which the form does correctly. This is however only applied to the formatting of the data when it gets displayed in the field, the data "behind" the field still uses "march 4, 2014", which you can see when you click on the field to edit the field contents.
You cannot change the way the data is stored when you export the data, and least not when you just export to a CSV file. If you have an external application (e.g. a VBA application that imports the data into Excel), you can of course apply any conversion routines you like. I've done this a number of times with VBA import routines, and it's just a matter of expressing your conversion in VBA code.
Another option is to modify the data at the time the data is entered. You can - in a custom validation script - take the date, convert it to the mm/dd/yyyy format and assign that to the field. This way, you are actually modifying the data that's behind the field, and not just the formatting.
Another option is to require the user to enter the date as mm/dd/yyyy.
You can run a script in Acrobat that would reformat the contents of your date fields, but that would be specific to your form. This could be run in an Action for one or more forms before you export the data to CSV.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com