Every once in a while we encounter an issue where the time zone appearing on the forum for our members does not match their real time zone. There used to be a way for me to manually update a member's time zone in their profile (instead of having their time zone automatically detected), and that would resolve the issue in most cases. I can't find that option anymore-- is there a new place where I can manually update a member's time zone? 

There is no way in which to manually alter someones timezone. This is automatically done on the 4.x system. They would need to check on their own system for where the issue is there, as it can only really show incorrectly if the users system is incorrect