I think what defines a generation is what people saw and remember, not directly years. From a European perspective, Boomers saw the first step on the Moon and

I think what defines a generation is what people saw and remember, not directly years. From a European perspective, Boomers saw the first step on the Moon and May 68 events, their children ("Gen X") saw Chernobyl, the end of the Cold War and grew up with the Oil crisis and the constant warnings that pollution is going to be a serious problem if we don't do something (or rather, if we don't stop doing certain things). Their children ("Millenials") saw the second Gulf War and the collapse of the WTC.