I'm on a Mac.

I subscribe to the "This American Life" podcast -- a free weekly download of the NPR show. Many of these broadcasts are repeats, and I'd like to change the "Release Date" to reflect the original broadcast date of the episode.

Is there an easy way to do this?

I tried loading iTunes Music Library.xml into a text editor and altering the date tagged to the individual podacst in question. However, when I load itunes, my changes are overwritten.

I tried deleting the iTunes Library file, and then altering iTunes Music Library.xml, to see if iTunes would rebuild its data based on my alterations. No dice.

Any suggestions? Many thanks.