When viewing a Calender event scheduled with OWA or Outlook, Evolution does
not recognize a modified instance of a recurring event.

Outlook or OWA are capable of editing a single instance of a recurring
event.  Whereas Evolution you must make the event movable, in essence
creating a new event, and then editing the event.  By using this procedure
with Evolution the desired results are achieved and appear correctly in
Evo, OWA, and Outlook.

In Evolution, one should be asked when choosing to edit a recurring event,
if the changes should effect all the instances of the event or just the
single event as Outlook or OWA do.