I can't seem to find how to change the time zone on the forum. I looked in the profile options... nothing about it there. I also found the help page, but the part that mentions changing the time zone looks very outdated.
I thought the timestamps displayed automatically adjusted to your timezone (probably based on the location of your IP address) as long as you're logged in. Mine always display as GMT +10 and I know the forum wouldn't use that as the system default.