flutter_test_date_format.dart

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

void main() async {
  await initializeDateFormatting();
  runApp(TestDateFormatApp());
}

class TestDateFormatApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: TestDateFormatScreen(),
    );
  }
}

class TestDateFormatScreen extends StatefulWidget {
  const TestDateFormatScreen({super.key});

  @override
  State<TestDateFormatScreen> createState() => _TestDateFormatScreenState();
}

class _TestDateFormatScreenState extends State<TestDateFormatScreen> {
  String _curLocale = 'en_US';

  @override
  Widget build(BuildContext context) {
    final now = DateTime.now();

    final icuConstantNames = [
      DateFormat.ABBR_MONTH,
      DateFormat.DAY,
      DateFormat.ABBR_WEEKDAY,
      DateFormat.WEEKDAY,
      DateFormat.ABBR_STANDALONE_MONTH,
      DateFormat.STANDALONE_MONTH,
      DateFormat.NUM_MONTH,
      DateFormat.NUM_MONTH_DAY,
      DateFormat.NUM_MONTH_WEEKDAY_DAY,
      DateFormat.ABBR_MONTH_DAY,
      DateFormat.ABBR_MONTH_WEEKDAY_DAY,
      DateFormat.MONTH,
      DateFormat.MONTH_DAY,
      DateFormat.MONTH_WEEKDAY_DAY,
      DateFormat.ABBR_QUARTER,
      DateFormat.QUARTER,
      DateFormat.YEAR,
      DateFormat.YEAR_NUM_MONTH,
      DateFormat.YEAR_NUM_MONTH_DAY,
      DateFormat.YEAR_NUM_MONTH_WEEKDAY_DAY,
      DateFormat.YEAR_ABBR_MONTH,
      DateFormat.YEAR_ABBR_MONTH_DAY,
      DateFormat.YEAR_ABBR_MONTH_WEEKDAY_DAY,
      DateFormat.YEAR_MONTH,
      DateFormat.YEAR_MONTH_DAY,
      DateFormat.YEAR_MONTH_WEEKDAY_DAY,
      DateFormat.YEAR_ABBR_QUARTER,
      DateFormat.YEAR_QUARTER,
      DateFormat.HOUR24,
      DateFormat.HOUR24_MINUTE,
      DateFormat.HOUR24_MINUTE_SECOND,
      DateFormat.HOUR,
      DateFormat.HOUR_MINUTE,
      DateFormat.HOUR_MINUTE_SECOND,
    ];

    return Scaffold(
      body: SafeArea(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(16),
          child: Column(
            children: [
              DropdownButton<String>(
                value: _curLocale,
                icon: const Icon(Icons.arrow_downward),
                elevation: 16,
                style: const TextStyle(color: Colors.deepPurple),
                underline: Container(
                  height: 2,
                  color: Colors.deepPurpleAccent,
                ),
                onChanged: (value) {
                  setState(() {
                    _curLocale = value!;
                  });
                },
                items: DateFormat.allLocalesWithSymbols()
                    .map<DropdownMenuItem<String>>((value) {
                  return DropdownMenuItem<String>(
                    value: value,
                    child: Text(value),
                  );
                }).toList(),
              ),
              const SizedBox(height: 8),
              ListView.separated(
                primary: false,
                shrinkWrap: true,
                itemCount: icuConstantNames.length,
                itemBuilder: (_, index) {
                  final dateFormat =
                      DateFormat(icuConstantNames[index], _curLocale);

                  return Padding(
                    padding: const EdgeInsets.symmetric(vertical: 16),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        // Text('${index + 1}/'),
                        // SizedBox(height: 8),
                        Text(
                          dateFormat.pattern ?? '',
                        ),
                        const SizedBox(height: 8),
                        Text(dateFormat.format(now)),
                      ],
                    ),
                  );
                },
                separatorBuilder: (_, __) => Container(
                  height: 1,
                  color: Colors.black,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

en_US

LLL
Aug

d
18

ccc
Fri

cccc
Friday

LLL
Aug

LLLL
August

L
8

M/d
8/18

EEE, M/d
Fri, 8/18

MMM d
Aug 18

EEE, MMM d
Fri, Aug 18

LLLL
August

MMMM d
August 18

EEEE, MMMM d
Friday, August 18

QQQ
Q3

QQQQ
3rd quarter

y
2023

M/y
8/2023

M/d/y
8/18/2023

EEE, M/d/y
Fri, 8/18/2023

MMM y
Aug 2023

MMM d, y
Aug 18, 2023

EEE, MMM d, y
Fri, Aug 18, 2023

MMMM y
August 2023

MMMM d, y
August 18, 2023

EEEE, MMMM d, y
Friday, August 18, 2023

QQQ y
Q3 2023

QQQQ y
3rd quarter 2023

HH
11

HH:mm
11:05

HH:mm:ss
11:05:25

HH
11

HH:mm
11:05

HH:mm:ss
11:05:25

LLL
Aug

d
18

ccc
Fri

cccc
Friday

LLL
Aug

LLLL
August

L
8

M/d
8/18

EEE, M/d
Fri, 8/18

MMM d
Aug 18

EEE, MMM d
Fri, Aug 18

LLLL
August

MMMM d
August 18

EEEE, MMMM d
Friday, August 18

QQQ
Q3

QQQQ
3rd quarter

y
2023

M/y
8/2023

M/d/y
8/18/2023

EEE, M/d/y
Fri, 8/18/2023

MMM y
Aug 2023

MMM d, y
Aug 18, 2023

EEE, MMM d, y
Fri, Aug 18, 2023

MMMM y
August 2023

MMMM d, y
August 18, 2023

EEEE, MMMM d, y
Friday, August 18, 2023

QQQ y
Q3 2023

QQQQ y
3rd quarter 2023

HH
11

HH:mm
11:05

HH:mm:ss
11:05:32

h a
11 AM

h:mm a
11:05 AM

h:mm:ss a
11:05:32 AM