Selfies with Trump. (Jabin Botsford/The Washington Post)

I get mad about millennials for a different reason than most people of my generation (which is Generation X, apparently). I get mad about millennials not because they are young and I am not and therefore everything they do and like seems stupid and foreign to me. Or, anyway, I don't only get mad for that reason. I also get mad because the term "millennial" is itself a marketing construct with no real start or end.

For literally years I have been trying to make clear to people that the reason folks born in 1981 are never quite sure if they're a millennial or a Gen Xer or a whatever is because there is no set definition or time period for the generation. In 2014, I talked to the Census Bureau, which noted that only the Baby Boomer generation has a defined start and end point, thanks to an identifiable demographic footprint. Everything else is just sort of made-up.

In January of last year, I saw a shadow creeping over the horizon. Pew Research -- a very good research outfit that I cite regularly -- warned that the number of millennials in the country was about to pass the number of Boomers. This was a remarkable shift; for the first time, the largest generation in American history would no longer be the largest generation. The only problem, as I noted then, is that this shift had already occurred. If you use the definition set forward by demographer Neil Howe -- one of the the guys credited with inventing the name for the generation -- millennials were born between 1982 and 2004. Meaning that at the beginning of 2015, there were already far more millennials than Boomers.

Pew was using its own boundaries for "millennial," setting it between 1981 and 1997 -- a much narrower window. That's a smaller period than is used by, say, Wikipedia, which puts the end point at "around 2000." Since Pew used a smaller window, the number of people who counted as millennials was necessarily smaller. And, therefore, it hadn't yet passed the Boomers.

Until now! On Monday, Pew announced that the inflection point had been passed, according to new Census Bureau data (looking at age by year of birth, not generational size). More millennials than Boomers! Let a thousand thinkpieces bloom! The media -- including The Post -- wrote it up. Yum yum yum, millennials.

Nothing special happened yesterday, though. And if you change the start and end years for what counts as "millennial" -- which you're welcome to do -- you can see how the number of members of that group bends and flexes relative to the other generations.

What we can say with certainty is that the number of people under the age of 30 is far larger than the number of Boomers. Some of those under-30s are not millennials, either; they're members of a Generation-Without-A-Name. (By Pew's definition, incidentally, the post-millennials are also nearly as big a group as the Boomers, too.) The White House calls them the Homeland generation (which is creepy) and MTV calls them the Founders (which is dumb). That MTV wants to name that group shows why groups get named: MTV wants to show them ads.

If you want to stress out about how America is being ruined by young people, go nuts. But you're doing that independent of any actual switch being flipped in demographic data. "Millennial" is a vagueness, a cloud from within which young people jostle and whine. And yeah, there are a lot of them. But that's not new.