Hi Darius,
I assume they are camera jpeg files where the date in imprinted on the digital image.
You camera menu should have an option to switch this feature off but I expect you have a number of images where the damage is done.
You need an image editor with a "clone" facility. Cloning is where you are able to copy an area of the image to another part of the image to "cover it up".
For work like that I use Corel PaintShop Pro. It's a similar price to PS Elements but from what I've seen, has more features as well as being easier to use in some respects.
I've just checked, the Gimp has a clone tool, check this out:
http://www.novell.com/coolsolutions/feature/15037.htmlTerry