Parse RFC 822 date (and make timezones work)

Question

Just realized DateFormat is not caring about the time zone field. The two prints below will both output the same time.

import 'package:intl/intl.dart';

void main() {
  var formatter = DateFormat('EEE, dd MMM yyyy HH:mm:ss zzz');

  print(formatter.parse('Tue, 9 Jun 2020 19:46:10 +0000'));
  print(formatter.parse('Tue, 9 Jun 2020 19:46:10 +0200'));
}

Sadly, I can't use DateTime.parse instead as it only accepts ISO-8601 strings.

So that begs the question, how do I parse RFC 822 timestamps correctly in Dart?

Answer 1

As per jamesdin's comment, I couldn't find any other way than to do this manually. Ended up with:

const MONTHS = {
  'Jan': '01',
  'Feb': '02',
  'Mar': '03',
  'Apr': '04',
  'May': '05',
  'Jun': '06',
  'Jul': '07',
  'Aug': '08',
  'Sep': '09',
  'Oct': '10',
  'Nov': '11',
  'Dec': '12',
};

DateTime parseRfc822(String input) {
  var splits = input.split(' ');
  var reformatted = splits[3] +
      '-' +
      MONTHS[splits[2]] +
      '-' +
      (splits[1].length == 1 ? '0' + splits[1] : splits[1]) +
      ' ' +
      splits[4] +
      ' ' +
      splits[5];

  return DateTime.tryParse(reformatted);
}