There is actually a popup caption DATE option, that displays the image date formatted for humans:
Go to the page settings > gallery > popup > show caption, enable "date".
The reason it displays as you currently see, is because it's part of your image EXIF meta data, and X3 doesn't generally format the date here as it's technical data. Instead, if you enable the date option above, you may then want to hide the EXIF date from displaying if necessary.