This [interactive timeline|http://www.bbc.co.uk/history/british/launch_tl_british.shtml] on the BBC website allows for many of these possibilities. There are two primary time scales and the ability to zoom in on the detail view. In addition, the timeline shows the context in which events occur by displaying key epochs in history as the backdrop of the visualization. The reader can also take different tours through the site that highlight related events or search the site for events of interest. Unfortunately, in the overview, there is no information about the nature of the individual events - they are just shown as dots so you have to mouse over the event to read about it. Also, it’s difficult to re-locate an event that you have seen previously unless you know exactly when it happened.