(YouTube Link)
Artist Mark Formanek and his team of seventy assistants set up a huge wooden digital clock in a Rotterdam train station. It's completely manual and the digits must be changed every minute by the workers, which is precisely what they did for twenty-four hours. Video in Dutch (presumably).
http://www.gizmowatch.com/entry/huge-wooden-digital-clock-installation-shows-real-time-manually/ via DVICE
This project is part of the construction of the new central railwaystation in Rotterdam, it was done on top of the constructionsite.