PSE using import date as shot date?

I recently upgraded to PSE15. On adding new photos from a card reader and renaming them after the shot date, I see in the Organizer that my filenames reflect the correct date, but that today's date (i.e. the import date) is showing under the pictures as the shot date. Is this a bug, or how do I change this so that my pictures correctly sort by shot date? (This is a big problem at the moment since I uploaded several month's worth of pictures and now they all have the wrong shot date.)

Thanks!