DateJS is not working in 0.4.x - I'm now investigating it.
This is a simple NPM wrapper around the excellent datejs client-side library.
It modifies the Date prototype - this technique is looked down upon, but it's a very useful library.
See the datejs site for more information.
In the shell:
npm install datejs
In your app:
NPM package datejs v0.0.1 corresponds to datejs Alpha1. It hasn't changed for three years, so hopefully it won't be too much of a maintenance nightmare.
I've just included all of the non-US locales in lib - I've not written any way to access them yet.
What I'll probably do is create a wrapper which defaults to en-US, but can be called with other locales.
I am not the author of datejs. I'm just maintaining an NPM package of it, as I needed one.