Dude, it's all made up and there is no hard definition for the years of Gen X.

I mean if you really want to be pedantic about it, the people we call Boomers these days are the original Gen X.

The term Generation X has been used at various times to describe alienated youth. In the early 1950s, Hungarian photographer Robert Capa first used Generation X as the title for a photo-essay about young men and women growing up immediately following World War II. The term first appeared in print in a December 1952 issue of Holiday magazine announcing their upcoming publication of Capa's photo-essay.

Or maybe it's people born in the 1950s and 1960s?

The term acquired a modern application after the release of Generation X: Tales for an Accelerated Culture, a 1991 novel written by Canadian author Douglas Coupland; however, the definition used there is "born in the late 1950s and 1960s", which is about ten years earlier than definitions that came later.[16][17][13][18] In 1987, Coupland had written a piece in Vancouver Magazine titled "Generation X" which was "the seed of what went on to become the book".

Or maybe it's 1965-1980?

In the U.S., the Pew Research Center, a non-partisan think-tank, delineates a Generation X period of 1965–1980 which has, albeit gradually, come to gain acceptance in academic circles.

Or maybe it's "Gen X is whatever we decide it is."

The Brookings Institution, another U.S. think-tank, sets the Gen X period as between 1965 and 1981.[31] The U.S. Federal Reserve Board uses 1965–1980 to define Gen X.[32] The U.S. Social Security Administration (SSA) defines the years for Gen X as between 1964 and 1979. The US Department of Defense (DoD), conversely, use dates 1965 to 1977.[33] In their 2002 book When Generations Collide, Lynne Lancaster and David Stillman use 1965 to 1980, while in 2012 authors Jain and Pant also used parameters of 1965 to 1980.[34] U.S. news outlets such as The New York Times[35][36] and The Washington Post[37] describe Generation X as people born between 1965 and 1980. Gallup,[38] Bloomberg,[39] Business Insider,[40] and Forbes[41][42] use 1965–1980. Time magazine states that Generation X is "roughly defined as anyone born between 1965 and 1980".[43] George Masnick of the Harvard Joint Center for Housing Studies puts this generation in the time-frame of 1965 to 1984, in order to satisfy the premise that boomers, Xers, and millennials "cover equal 20-year age spans".[44]

In Australia, the McCrindle Research Center uses 1965–1979.[45] In the UK, the Resolution Foundation think-tank defines Gen X as those born between 1966 and 1980.[46] PricewaterhouseCoopers, a multinational professional services network headquartered in London, describes Generation X employees as those born from 1965 to 1980.[47]

But those are just think tanks. Surely other experts have a specific range, right?

On the basis of the time it takes for a generation to mature, U.S. authors William Strauss and Neil Howe define Generation X as those born between 1961 and 1981 in their 1991 book titled Generations, and differentiate the cohort into an early and late wave.[48] Jeff Gordinier, in his 2008 book X Saves the World, include those born between 1961 and 1977 but possibly as late as 1980.[9] George Masnick of the Harvard Joint Center for Housing Studies puts this generation in the time-frame of 1965 to 1984, in order to satisfy the premise that boomers, Xers, and millennials "cover equal 20-year age spans".[44] In 2004, journalist J. Markert also acknowledged the 20-year increments but goes one step further and subdivides the generation into two 10-year cohorts with early and later members of the generation. The first begins in 1966 and ends in 1975 and the second begins in 1976 and ends in 1985; this thinking is applied to each generation (Silent, boomers, Gen X, millennials, etc.).[49]

https://en.wikipedia.org/wiki/Generation_X

This isn't science, it's categorization based on pretty arbitrary stuff.