Tic Toc, Tic Toc

I wish I had something interesting to report for today but it was a slow (painfully slow) and absolutely uneventful day. What is it that makes the weekend fly by but when you're at work (whether it's in an office or at a grocery store) time stand still in the middle of the day or the middle of a four hour shift? It's like a miracle of physics or something--when I step into the grocery store to go to work 4 fours feels so long it's like 4 days.