Someone asked a question about how frequently young people have time to socialize and it made me think about what people do with their evenings. I recently asked my son to go to a concert (free ticket to see a band i know he likes) and he declined because it was an hour away on a weeknight. If we invite our kids or niece/nephew to dinner they always want to go at 6/630 which feels so early. Edit: Kids are 30ish.
I believe this is an argument about 1900s meaning the decade or the century.
To this, I believe, the perfect answer is: https://english.stackexchange.com/a/958
That was 10 years ago. The further we get from “the 1900s” the broader the term will become to include the whole century, much like the 1800s is 1800-1899. I imagine in another 10-20 years it will be more and more common to see this shift when referencing past events.