1981 is at least 7 years too early. If you have ever done these things, you are probably not a millenial: 1) Called your friend using the number you found in the phone book, and talked to their parents to ask if they were home; 2) Used a card catalog; 3) Correctly capitalized and punctuated a sentence; 4) Acquired a marketable skill.
Those dates are the official ones. It's considered to be anyone reaching adulthood in the early parts of the century. I mean, you can certainly disagree but I'm going to want to see your sources. https://en.wikipedia.org/wiki/Millennials
Possibly it's time to just give up and let "millennial" mean "kids these days" and come up with a different name for the generation that came of age at the turn of the millennium, since that is how 70% of people and 100% of angry thinkpieces about Kids these Days use it anyway.
But 'kids these days' just lacks that scientistic gleam that makes the rant seem knowing rather than dumb. I was thinking recently that nobody talks about Generation X any more. I don't see any think pieces talking about how 40-50 year olds are cynical slackers even though it was self-evidently true when they were 'kids these days'.