Demographically it's an exercise that's kind of interesting to me.
Strauss and Howe, the guys who brought us the term "Millennial" and also Steve Bannon's apocalyptic worldview, broke shit up into "saeculums" by blaming it on the Romans. They didn't go as far as pointing out that the Chinese zodiac uses the same basic idea except instead of 20 years they went with 12.
Probably because if you go with 12 the whole idea of "generations" is blown to shit.
Either way, I think there's a lot more credo to the notion that different people end up with similar drives and ethics when they grow up in similar environments and if you're all in 4th grade when the Challenger blows up you're going to have a slightly different reaction to it than if you were all in 10th grade and a very different reaction if you were all in grad school. Is it 12 years? Is it 20? It's probably neither and both and the individual differences are enough that they likely drown out anything you can determine from the similarities.
The fact remains, however: 'boomers ragged on Generation X and Millennials. The 'boomers birthed the Millennials but GenX were those annoying neighbor kids they had to pay too much for babysitting their brats. That's a half generational step, more like a Chinese zodiac cycle than a saeculum.
And really, the whole argument of generational theory is that your life is going to be very different if you're anchored at "a car costs a summer job" than "a couch is three months salary".