you could use, LEFT and RIGHT functions to split the Date ID & then Concatenate it into a string of format mm/dd/yyyy. Then go to your Dimensions pane and convert the format type to date.
I tried that earlier. It does not allow me to do a left or right function (calculated column) on a dimension
hmm, Thats odd. essentially you should be able to make 3-4 calculated fields based on how you split things & then put it together as a string. could you share a screenshot of the code you are using and the exact error you get?