unpopular opinion:
Millenials are 1981-2007 (from microcomputer to GFC and Web 2.0), 26 years
Zoomers will be 2008-2038 (from GFC to ❔), 30-ish years
"Alphas" are ten years away.
Gen length increases because it takes longer to build a life/family, if you even can, in the 21st century. May change dramatically for the better after ❔
thing is, 1981-1994 makes no sense for a "generation" (you don't have kids at 15 yo lol). So 1981-2005 is more like it (24 years, that's more like it).
Gen Z is far from being identifiable yet, but most likely something like 2006-2030 or so.
It's just that marketing and the media always want to make you believe there's a new hot thing but no, 17 or 15 years is not a full generation, whether biological or in the Strauss–Howe sense of that theory. These shorter bouts are more like cultural trends, good old decades, and they do overlap or vary by country.