they clearly identified which was the old and which the new schedule. Here's an example:

Sat, Jan xx, 2007 - Washington, DC (IAD) to Los Angeles, CA (LAX)

United 0824 Depart: IAD 08:35 AM
Arrive: LAX 10:59 AM Non-stop
5h 36m
763
2,288 miles traveled Booking class: W
Economy
2288 Award miles
Food for Purchase Flight: Schedule change
Upgrade: Pending
{Seat assignment}
Download to calendar




Sat, Jan xx, 2007 - Washington, DC (IAD) to Los Angeles, CA (LAX)

United 0824 Depart: IAD 08:40 AM
Arrive: LAX 11:16 AM Non-stop


2,288 miles traveled Booking class: W
Economy
2288 Award miles Flight: Schedule change
{Same seat assignment}
Download to calendar

Each entry is essentially identical except for the times. How hard would it be for the first to say "original schedule" and the second to say (as they BOTH do) "schedule change"?