This is actually set in your profile.
Follow these steps to correct it:
1) Go to: Profile > Look and Layout Preferences
2) Look for:
"Time Offset:
Number of hours to +/- to make displayed time equal to your local time."
3) Next to the box with the number of hours, you will find a link which says "auto detect". Clicking on this runs a javascript which detects your computer time.
4) Alternatively, you can manually enter the number of hour difference in the box by putting tthe number of hours you are ahead or behind of the forum time (the current forum time is displayed below the box).
5) Be sure to scroll down and click the "Change Profile" button at the bottom to save your changes.