Here Is When Each Generation Begins and Ends, According to Facts - The Atlantic

Baby Boomers. This is the agreed-upon generation that falls within DiPrete's punctuated timeframe. It began when the Greatest Generation got home and started having sex with everyone; it ended when having sex with everyone was made easier with The Pill.
Generation X. George Masnick, of the Harvard Joint Center for Housing Studies puts this generation in the timeframe of 1965 to 1984, in part because it's a neat 20-year period. He also calls it the "baby bust," mocking "[p]undits on Madison Avenue and in the media" that call it Generation X. Ha ha, tough luck.
Generation Y. Masnick addresses this group, too, putting it "anywhere from the mid-1970s when the oldest were born to the mid-2000s when the youngest were." But mostly Generation Y is a made-up generation when it became obvious that young kids didn't really fit with the cool Generation X aesthetic but not enough of them had been born to make a new generation designation. NOTE: Generation Y is a fake, made-up thing. Do not worry about it.
Millennials. In October 2004, researchers Neil Howe and William Strauss called Millennials "the next great generation," which is funny. They define the group as "as those born in 1982 and approximately the 20 years thereafter." In 2012, they affixed the end point as 2004.
TBD. But that means that kids born in the last 10 years lack a designation. They are not Millennials. Earlier this month, Pew Research asked people what the group should be called and offered some terrible ideas. In other words, this is the new Generation Y. We'll figure out what they're called in the future.