Major events in history shape people differently

Major events in history shape people differently depending on the life phase they occupy. As people are shaped, they sort themselves into different generations. To belong to the same generation, a group of people must feel a unique location in history, share distinct beliefs and behavior, and perceive a common group membership. They must also be able to inhabit the same life phase at the same time—which is why a generation comprises roughly 20 to 22 consecutive birth cohorts. (A birth cohort is everyone born in the same year.) Source