Well, this is the internet - that clock will never be right for more than a small amount of people. If you still want to change it, you'll need to hack the source a bit.

Open up wakaba.pl or kareha.pl, find the post_stuff() function, and change this line (this is taken from kareha.pl, I think wakaba.pl is the same):

my $date=make_date($time,DATE_STYLE);

to something like:

my $date=make_date($time+7*3600,DATE_STYLE);

Or whatever it should be to show the time you want.