Probably a setting on the forum server clock.
I am in Perth, if I make a post at 8 am in the morning, the forum timestamp on the top left hand corner of each post would show "11 pm yesterday".
It should show "11 am(AEST) today".
So even though posts are made in the morning today, they are shown as being made yesterday. And this applies to posts made by anyone from anywhere in OZ.
