When you hover over the saturday box, the following sunday jumps over to the saturday column and the rest of the dates jump down a line and shift to the left.
I was viewing the site on a mac, OS 10.6.8 using Chrome (version 23.0.1271.101). I don't think it is still a problem. I just figured out that it only happens if the upper frame from Themeforest is still active. Once you remove the "Purchase This Item" frame, the issue goes away. I should have known better. That frame causes all sorts of issues when previewing themes.