Time mismatch when using "time difference"

My server runs in UTC time, while the forum should run in CET. So I changed the forum setting "Time difference: Time difference between server and forum time in minutes" to 60 minutes. All seems OK, but when opening a message with replies in threaded mode, the list in the "Complete thread:" part still bear the UTC time.

Otto

Complete thread:

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Time mismatch when using "time difference" - Otto, 2008-02-07, 20:28
- Time mismatch when using "time difference" - Otto, 2008-02-08, 20:52
- Time mismatch when using "time difference" - Alex, 2008-02-08, 21:38
  - Time mismatch when using "time difference" - danky, 2008-02-10, 03:03
  - Time mismatch when using "time difference" - Otto, 2008-02-10, 06:46
  - Time mismatch when using "time difference" - bttr, 2008-02-12, 09:10

my little forum

Time mismatch when using "time difference" (Bugs)