How to load all dart DateFormat locale in flutter?

I solved it setting the Intl.sytemLocale before using any DateFormat:

Intl.systemLocale = await findSystemLocale();

I didn't had to call initializeDateFormatting() and I'm using intl: ^0.17.0.

In your highest StatefulWidget add these imports

import 'package:intl/intl.dart';
import 'package:intl/date_symbol_data_local.dart';

in its State, override initState and add

  void initState() {

For example

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:intl/date_symbol_data_local.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Intl Demo',
      theme: new ThemeData(
      home: new MyHomePage(title: 'Intl Demo Home Page'),

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  _MyHomePageState createState() => new _MyHomePageState();

class _MyHomePageState extends State<MyHomePage> {
  DateFormat dateFormat;
  DateFormat timeFormat;

  void initState() {
    dateFormat = new DateFormat.yMMMMd('cs');
    timeFormat = new DateFormat.Hms('cs');

  void _refresh() {
    setState(() {});

  Widget build(BuildContext context) {
    var dateTime = new;
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      body: new Center(
        child: new Column(
          children: <Widget>[
            new Text(dateFormat.format(dateTime)),
            new Text(timeFormat.format(dateTime)),
      floatingActionButton: new FloatingActionButton(
        onPressed: _refresh,
        tooltip: 'Refresh',
        child: new Icon(Icons.refresh),

Dart mostly uses the ISO 631 2 letter codes, with country variants if applicable. For example: ja, en_US, en_GB, zh_HK, zh_CN. Occasionally it uses a 3 letter code. To find the full list just search for DateSymbols in the file date_symbol_data_local.dart

The cs language displays this

The list of all available locales in Flutter can be take from top-level property availableLocalesForDateFormatting of intl package.

final availableLocalesForDateFormatting = const [