I was talking to someone (younger, obviously) and they used the phrase "in the late 1900s" completely unironically. It stopped me dead in my tracks and took my brain about 5 seconds to compute. By the time I was able to speak again, the only thing I could say was "you need to shut the fuck up and leave right now."
As an elder millennial (84, fuckers) I'm really struggling with entering middle age. But I guess I just approach it the same way my generation has approached everything else, with a weird mix of existential dread and wry humor (hat tip to Gen X for starting that, though).