A few years back, a friend was talking to me and used the phrase, "Middle-aged people like us." It was one of those phrases that made me stop listening to whatever else he was talking about. I looked around and noted that only the two of us were present. I realized with shock that my friend thought that I was middle-aged. I received a second shock when it occurred to me that my friend was right.
I suppose another indicator that I am aging happens when I'm around teenagers...