Are you syncing through Exchange? I see the same issue......of course the HTC clock widget also used to think I was in Portland Or instead of Portland CT so, an hour off wasn't too bad.
That said, a lot of my appointments are screwed up on the Eris....some that recurr on scheduled such as "first of each month" or "first wed of each month" Simply show up every day....Others have gotten scheduled mutliple times and some, as in your case, show up an hour early.
Hoping this all gets cleaned up through an update either this month or next. Guess it could be worse and they could remind us an hour late :-/