Where are you looking for this information?
There are two kinds of metadata involved when you consider jpeg or other image file.
One is the file data. This is what the Finder shows. This tells you nothing about the contents of the file, just the File itself.
The problem with File metadata is that it can easily change as the file is moved from place to place or exported, e-mailed, uploaded etc.
Photographs have also got both Exif and IPTC metadata. The date and time that your camera snapped the Photograph is recorded in the Exif metadata. Regardless if what the file date says, this is the actual time recorded by the camera.
Photo applications like iPhoto, Aperture, Lightroom, Picasa, Photoshop etc get their date and time from the Exif metadata.
When you export from iPhoto to the Finder new file is created containing your Photo (and its Exif). The File date is - quite accurately - reported as the date of Export. However, the Photo Date doesn't change.
The problem is that the Finder doesn't work with Exif.
So, your photo has the correct date, and so does the file, but they are different things. To sort on the Photo date you'll need to use a photo app.
If yoy are seeing this in iPhoto then you did not get the correct photo from your PC - iPhoto uses the EXIF and IPTC data which is inside the photo and was originally placed there by the camera - it sounds like your PC did not keep it intact
If you ae seeing it in the finder then you are looking at the file metadate rather than the photo metadata - look in iPhoto or using Preview to see the photo metadata