I guess I'm not sure what you mean. The forum doesn't have or need a time setting. It merely has to save all the message times in the same time zone and format so it can convert the times to whatever time zone the reader happens to be in.
If you live in GMT-5, but you have your time zone setting on your Profile page set to GMT-7, all the messages will appear to have been posted 2 hours LATER than they actually were. For example, after you post a new message, go check the time it was posted. If your time is set incorrectly as in my example above, the message will appear to have been posted almost two hours in the future, even though you just posted it a few moments ago.
Go to your Profile
page, change your time zone setting to your local time zone, and everything will appear correctly.