Default locale not being picked up

Expected behaviour

Using setDefaultLocale to en-GB, I would expect the default locale to be the the en-GB format (day/month/year)

Actual behaviour

Display in the en-US format (month/day/year)

Steps to reproduce

Minimal app:

import React, { Component } from "react";
import ReactDOM from "react-dom";
import Datepicker, { registerLocale, setDefaultLocale } from "react-datepicker";
import "react-datepicker/dist/react-datepicker.css";
import { enGB } from "date-fns/esm/locale";

registerLocale("en-GB", enGB);
setDefaultLocale("en-GB");

class App extends Component {
  render() {
    return <Datepicker selected={new Date("2018-12-30")} />;
  }
}

ReactDOM.render(<App />, document.querySelector("body"));

Package.json

{
  "name": "react-datepicker-test",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "react": "^16.6.3",
    "react-datepicker": "^2.0.0",
    "react-dom": "^16.6.3",
    "react-scripts": "2.1.1"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": [
    ">0.2%",
    "not dead",
    "not ie <= 11",
    "not op_mini all"
  ]
}

Screenshot:

Printing getDefaultLocale() in the render also correctly prints en-GB.

[MickMonaghan]

This is a significant issue. Changing the locale should by itself be enough to change the presented format. Looks like this applies for all locales - not just en-GB. One should not have to set the dateFormat manually. The locale data imported from date-fns looks like it should be adequate - here’s the en-GB data: https://github.com/date-fns/date-fns/blob/master/src/locale/en-GB/_lib/formatLong/index.js#L7

[tombiddulph]

For whatever reason the dateFormat prop is still set as MM/dd/yyyy when the locale is set to en-GB. https://github.com/Hacker0x01/react-datepicker/blob/93d4694c50cb894edb3884f802537feeec4c4c66/src/index.jsx#L85

Setting the dateFormat prop to dd/MM/yyyy resolves the issue with or without the locale set to en-GB

class App extends Component {
  render() {
    return <Datepicker 
                   dateFormat="dd/MM/yyyy"
                   selected={new Date("2018-12-30")} />;
  }
}