You may find that, when your region changes from Daylight Saving Time (DST) to unadjusted time or back, the time shown in the forum (at top left) becomes incorrect by one hour.
This is because every user has their own time zone and separate DST flag. The DST flag is not adjusted automatically - every user has to change this when their own local time moves into or out of DST. While this is rather annoying I can see why it is - different areas of the world have varying DST arrangements or no DST at all, so it would be more-or-less impossible for the board to make the adjustment for you automatically.
To change your DST setting, go to the User Control Panel (link at top left, just below "Board Index"). Select the "Board Preferences" tab, the 'DST is in effect' selector is near the bottom, just below your time zone. Alter the DST selector to match your situation and press 'Submit' to change your setting.