There doesn't seem to be anywhere on a Blackberry to set Daylight Savings Time. I am in the UK - currently BST - so if I choose the option for Dublin, London (GMT) I am an hour out.
This does not seem to affect individual timed events that are synced from my Exchange Server, but all day events sometimes show as starting an hour into the day and 'bleeding' over an hour into the next day.
I can fix this by "telling" the Blackberry that I am in West Africa (GMT+1) but I shouldn't have to do this. (My phone has a Daylight Savings time option, so I am not sure why I don't have one here.)