Sometimes I get +7 hours timestamps in chat:
(note that I took screenshot 5 minutes after they appeared, so it was exatly 7 hours shift initially)
+7 is my local timezone. Idk how it happens - sometimes right after log in, sometimes during the play.
They always stay at bottom of chat window until 7 hours passed or client restart.
Also when chatting in party, messages sometime show in a bit different order. I guess it depents on local time of participants? It could be related to this problem too.