Dependent on where you server is, you will have to change some hardcoding within the files themselves. The forum you should be able to change within the forum admin cp.
I can't remember which files you have to modify to change time and date in all places, maybe someone else remembers. There are a few of them, news, downloads, stats etc
Read this, it explains "setlocale" for time function
http://ca3.php.net/manual/en/function.strftime.php
good luck, hope this helps