As david63 points out, user action is required after the upgrade to phpBB 3.1 to change their settings to make the new automatic DST feature work. We've made it part of the "announcements" we make when upgrading a forum to phpBB 3.1.
Part of the challenge is how phpBB presents the timezone information in User Control Panel->Board preferences (direct link is ucp.php?i=165
) in the My timezone
The important user step is to set the country/city pair (2nd dropdown), which enables the automatic DST feature to work.
Normal people… believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet. – Scott Adams