Strongly disagree.

Who maintains day.js? It‘s (i did not look, i guess) not the same people that develop the JavaScript standard library. At some point, day.js is abandoned or breaks something and nobody is going to fix it because it is abandoned, or even worse, soneone creates a fork and fixes it there and now we have 2 day.js.

If it is in the standard library, you have a guarantee that it works today, works tomorrow and with a quite high certainty still works the day after. There are not that many languages that successfully break backwards compatibility often.

And don‘t get me started with the legal aspect. There are many projects where one cannot simply pull another dependency just to calculate a date diff.

What makes the Date constructor a good candidate for the standard library but not the aforementioned methods? Not everyone knows about Day.js, you had to learn that at some point. Why Day.js instead of Moment or Luxon or Date-Fns? There's a lot of cognitive value to having a fully featured standard library.

That why we read and learn. You can't expect node to work like java. I feel like I'm talking to a wall with you guys. I've been working with JS for 15 years. I would never presume to start Java dev and expect to do things my way. I saw the same thing when Java devs were trying to learn Ruby... you have to approach with a different mentality.

Regarding Moment, on their site and they plaster exactly why you should not use moment and explain exactly why other libs (Day.js included) are better. Node is designed to be modular, Java isn't.

That‘s not the point. Nobody expects that Node/Js does exactly the same as Java or C#. If so, one could simply use Java or C#.

A language should provide a set of functionality that makes the developers life easier and consists of a set that he can achieve basic (daily) things without the need of 3rd-party dependencies. And if that usually starts with „npm -i“ I‘m going to question that...

We are going to have to agree to disagree then. Both Node and frontend js share the same package management system (npm). Everything is modular because it has to be. When you work fullstack JS and use one package manager for everything, it makes all the sense in the world why things are done the way they are. The same code has to work in Node, Blink, Webkit, Electron, etc.

Node's lack of a robust standard library results in significant dependency bloat, even for small projects. I often choose other languages (Racket, Python) for most projects because of this. I tend to consider a large number of dependencies as a risk for the stability and maintainability of projects. Through this lens, adding date handling to the standard library can make sense, I think.

I think others think differently https://tc39.es/proposal-temporal/docs/