There is a lot to like about the LongViewer. Firstly it's open source, which means we can all peak around and adapt the code. Secondly it comes with a prestigious heritage: The Long Now Foundation are a fascinating not-for-profit organisation aimed at encouraging long term thinking.Both the live examples look great and according to the documentation they can be easily styled with CSS.
The two most interesting interface features are the macro view and the 'now' indicator. The 'now' indicator is a dynamically rendered line that clearly delineates past, present and future. The macro view is an interface element for quickly navigating the length of the main timeline.