The "20th anniversary of 9/11 on TV" thread got me wondering about how other anniversaries of big historical events have been covered on TV. I remember a flurry of programs on the 20th anniversary of the JFK assassination in 1983, and to a lesser extent the 40th anniversary of D-Day the next year. But I don't remember if the actual days had pre-emptions for memorials and the like. What do you remember of historical anniversaries on TV in the past?