You may have to log out and log in after saving changes to your preferences.
Your time-zone preferences only apply when you are logged in, not when you're lurking as a guest.
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Also, the time-stamps on the most -recent-post list on the left of the AC screen may not match the time-zone in your preferences.
Your preferred time-zone may apply only while viewing the actual posts.
For example, the post that I'm replying to at about 1:00 my Denver time is from Jimmie.
When I view Jimmie's post in the thread, the post correctly shows that it appeared at my preferred 12:43pm Denver time.
But the most-recent-post list on the left-side shows that Jimmie will use a time machine to post it two hours later than now at 2:43pm.
