Try logging out, clearing all cookies for PB and logging back in.
So, I did this. When I logged back into PB and clicked "Today's Posts" for a quick second, the time stamp appeared next to "Today" and then disappeared. However, when I resized my window (I made it wider), lo and behold, there is the time stamp again! So, I guess it was a window size thing? And maybe a cookie thing, too?