Change properties of iMovie Events

I have old VHS tapes from 1998 that I copied to digital 8mm in 2003. Now all of them have been digitally dated as 2003, not 1998 and I want them organized and stored in m y 1998 folder in the iMovie Events Library. How can I change the date in the events, or the clips" so that I can have them appear in the right place in the Event Library.?