Changing the date on digital photos?

A bit of blegging -- that's what you call begging on a blog -- if you don't mind. We have a couple of Kodak digital cameras and they both have the annoying habit of reverting to default date and time when the batteries are out for recharging. Of course, we don't usually remember to reset the date and time until we've taken a couple of dozen pictures. When we look back at our digital archives in 20 years or so January 1, 2004 will look like a very busy day.

I'd like to go back and change the file date and/or the embedded "taken on" date for these photos to the actual date while I can still remember what it is. Anyone know of an easy -- and preferably free -- way to do this?