The longest movie ever is over 10 days long!

It's called 'Modern Times Forever' and it's an experimental film that was projected on the side of the Stora Enso building in Helsinki, Finland.

The film shows the decay that would happen to that building over thousands of years, compressed into a 'shortened' 10 day sequence.

The film took the crown away from the previous longest film, Cinématon. That film was a project by the director where he gave his friends each 3 minutes to do whatever they wanted. That film ran for 167 hours.

(Source)