Ah, the Fourth Turning - great theory! (I read their earlier Generations.) The turnings don't have anything to do with numerology or fixed physical cycles; rather more the average length of a human generation x 4.
I think our generational crisis was clearly 9/11. What makes it a generational crisis is that it's an event that triggers a sea change in generational attitudes, which had been gathering already. It's not the crisis itself, necessarily, that defines the generational turnings. It's how the dominant generation reacts to it. When a generation is primed to cause a turning, sooner or later some crisis comes along that the generation responds to in a fundamental way, as opposed to brushing it under the rug.
Presumably if 9/11 had happened at a different point in the cycle, it would have been treated as merely a huge criminal act, like some on the left wanted, instead of the opening shot of WWIII, which it really is.