Somebody painted a shadow? Is it their version of a sundial? Is it always quitting time? :)
I'm pretty sure (and I had to a lot of mental images for this) that no matter where you stood, the image would never be at 5 o'clock.
Have you seen the movie Exit Through the Gift Shop? It's a pretty good documentary about street art.
It's on my list at Netflix. A friend who shares my taste in books and movies recommended it.