...when you start telling "When I was a kid..." stories.
Like, "When I was a kid, every store wasn't air-conditioned."
..."our hardware store had wooden floors."
..."an old guy in an old pickup used to sell apples door-to-door"
..."cars driving through town had running boards on them."
..."city street projects had smudge pots around them at night instead of blinky lights."
and one of my personal favorites..."there were only four kinds of breakfast cereals in the stores."