Setting the date and time values for PNG, JPEG, and TIFF image files is simple with Image Redate. It's simple:
Image Redate changes the "Exif Date Time Original" metadata, and if there’s TIFF metadata, the "TIFF Date Time" metadata is also set. The file’s creation date is not changed. The Exif date is the date apps such as Photos and iPhoto use when displaying image dates. For example, you scanned an old photo of Woodstock, but you don't want the photo date set for today, you want the date set as August 15, 1969. Redate can change the date in 3 easy steps!
Note: Currently available for $0.99