Comment 1 for bug 286567

The problem is that KDE 3 didn't store the timezone along the time, so KDE 4 apparently assumes it is UTC and does the default operations for not-locale times, it translates them into your locale one.
However, the entry in the calendar file itself is not changed, and the general assumption seems to be that editing an entry should by default use the entries time in a non localized manner (or maybe that just applies to such entries without time zone definition).

Anyway, I am not sure this actually should be changed/can be changed in a sensible way. There probably are cases where you want to keep a UTC using file. KOrganizer can't determine if the file is applying to that use case, of it is just a KDE 3 one.
So my point of view is that as long as the event shows correctly in the calendar view this issue is only of very minor importance, recurring ones, which would be most affected I guess, would only need to be canged once anyway.