In cultural terms, I have always felt that the 1960s began on the day Kennedy was assassinated (November 22, 1963), and ended the day Nixon resigned (August 8, 1974). Others have dated the beginning of the 1960s to February 7, 1964 — the day the Beatles landed in New York.
In the future, what day will people choose as the beginning of the this, the first decade of the 21st century? It’s hard to argue with September 11, 2001, but the date that stands out in my mind is November 8, 2000, when it became clear that the presidential election was essentially tied. Although Bush eventually won, his presidency was forever tainted by the original sin of having to go to the Supreme Court to secure the victory. This event had an impact on nearly everything Bush did, and on most US policy, including the response to 9/11.