I found these poll results super interesting. I tend to think of nostalgia as something "for old people." Old people have a wider variety of things to be nostalgic about.

But, many people responded that they experienced nostalgia before turning 10 years old.

@nprofile1q... wisely observed that nostalgia isn't just about time, it can be about a place or a country.

And most seem to find nostalgia less appealing as we age, in the comments the comercialization of the past was a big factor in this.