I remember that for my 1st AONEx in 2002, AA required a ticket reissue for a date/time change. Then, they were concerned about stickers on paper tickets. But it was a pain as I had more than 16 segments and the city ticket office found some way to get the printer to print the entire new ticket. No fee charged though. Reissueing an e-ticket should be very easy for date/time changes though.