A few weekends ago, I went down to an all-night showing of Christian Marclay's 'The Clock' at Tate Modern. It is a difficult thing to explain, and the reality is different from what you expect, but if you are ever in a place where it is showing, it is worth getting in to see some of the film, although you probably won't watch all of it in one go.
The film lasts 24 hours, and features scenes from hundreds of films where a clock is visible or the time is referenced in the dialogue.
Details of the Tate exhibition are here.
Here's a PODCAST on the making of the film
And here's what you see when you go inside...