date.js

Before date-fns, before day.js, before Luxon, there was date.js. Matthew Mueller wrote it as a single-file drop-in replacement for the awful Date API. `new Date().strftime("%Y-%m-%d")` just worked. It had sugar like `Date.today()`, `Date.tomorrow()`, `Date.parse("3 weeks ago")`, and a fluent API for relative dates. It peaked around 2010 with 1.5k stars and a permanent spot in every "JS date utility" comparison blog post. The repo went quiet in 2022. date-fns won the category. But if you've ever debugged a timezone bug in day.js, you know there's still a place for a single-file vanilla solution that doesn't pull in 80kb of dependencies.