When did “millennials” get redefined?

“Generations” for grouping (vs ancestry) have been roughly 15 year spans. Generation X was the 1970s through about ’85. After that was Generation Y. Millennials, by definition, were people born at or after the turn of the millennium. Being generous, that could be as early as ’98.

Now, people are trying to say Gen-X included the ’60s, and that Millennials are in their 30s.

Nooooo! That is inaccurate. Labels matter, and some media or researcher does not get to redefine people after the fact to fit their narratives!