|You might be getting too hung up on those "dates", as such properties can even be modified artificially (an old Explorer shell extension called Properties Plus has long been able to do just that).|
Further to my earlier general statement regarding the Exif data being lost on modification of a photo file, I must add that some (most?) graphics programs give the option to keep or toss that data when saving. Even Fax and Picture Viewer retains the Exif info even after rotating it. Copying to CD utilities often give to option to retain original times/dates, and if the Exif is present, that too will automatically be included.
But once The Exif data is missing, I don't know of any way to retrieve it.... although I have never investigated that point.