I've had discussions about this in the SB before...
I went and tested a theory using my own profile and worked it out - it seems that the post stats are calibrated individually but you have to make sure the boards know your timezone.
Dirigible, to update this - Go to your Profile then select 'Look and Layout' from the menu on the left hand side. In the options that come up, find time offset and click 'auto detect'. Save those changes and see if the time in the upper right corner above the SB is right - if not, alter the time offset to suit and save it again.
After you've got that all sorted out, go and look at your post stats and they should be accurate for you.