I had a similar issue.

This will NOT fix what's on the recorder!!! But I was able to get my images (pictures) and used EXIF editor to change the date and times.

-> Since I see the HDR has a few video formats I can't guess which one you use on your PC but read http://www.bricecenter.com/how-to-reviews/photography/change-taken-date and see if that does the trick.
bob