This is the definition I found: "born between 1977 and 1983. ... It's a population sandwiched between Gen Xers and millennials that doesn't identify with either." I think geriatric millennials are those born from 1980 to 1985 so yes, an overlap there. I don't take any of it too seriously. I mean, it's all a bit silly right? By this definition my husband isn't actually a geriatric millennial after all! (he was born 1990).