Did you notice if it used to be correct, but for some reason it changed, or did you notice when it became off by one hour?
You can check the time which is set in your profile. If it is not correct there, then you can fix it. If it is correct, but only your sweeps check is not right, then I guess you can submit a ticket to the help desk.
I would start with your time setting. Here's how (in case you haven't tried yet):
When you are in the forum, go to Forum Actions and choose Edit Profile.
That takes you to your profile.
Along the left on your profile page, there are 3 boxes. Choose the third box, My Settings, then My Account, then General Settings. Scroll all the way down to Date and Time Options, where you will see a box to choose your time zone. You can change it if it is wrong, and save.
(I don't know if this is necessary, but after changing the time and saving, I would refresh, then see if sweeps check is showing the correct time.)
If you did all of that, and you still need help, please submit a ticket to the help desk:
http://www.sweepsadvantage.com/hesk22/