/// Get date as a string for display.
String getFormattedDate(String date) {
  /// Convert into local date format.
  var localDate = DateTime.parse(date).toLocal();

  /// inputFormat - format getting from api or other func.
  /// e.g If 2021-05-27 9:34:12.781341 then format must be yyyy-MM-dd HH:mm
  /// If 27/05/2021 9:34:12.781341 then format must be dd/MM/yyyy HH:mm
  var inputFormat = DateFormat('yyyy-MM-dd HH:mm');
  var inputDate = inputFormat.parse(localDate.toString());

  /// outputFormat - convert into format you want to show.
  var outputFormat = DateFormat('dd/MM/yyyy HH:mm');
  var outputDate = outputFormat.format(inputDate);

  return outputDate.toString();
} 

处理年度季度，从字符串到日期时间，我没有找到合适的解决方案，所以做了这个:

    List<String> dateAsList = 'Q1 2001'.split(' ');
    DateTime dateTime = DateTime.now();
    String quarter = dateAsList[0];
    int year = int.parse(dateAsList[1]);
    switch(quarter) {
      case "Q1": dateTime = DateTime(year, 1);
      break;
      case "Q2": dateTime = DateTime(year, 4);
      break;
      case "Q3": dateTime = DateTime(year, 7);
      break;
      case "Q4": dateTime = DateTime(year, 10);
      break;
    }

import 'package:intl/intl.dart';

main() {
  var formattedDate = new DateTime.Format('yyyy-MM-dd').DateTime.now();
  print(formattedDate); // something like 2020-04-16
}

有关更多详细信息，请参阅DateFormat文档

由于flutter常用的Datetime库不知道德国的区域设置——de、de、de_DE、de- de或任何其他组合都不知道，例如，如果您希望用人类可读的字符串编写月份名称或日期名称，我建议您使用以下代码。

安装pub flutter pub add date_format

String formattedDate = formatDate(DateTime(year, month, day),[dd,'. ', MM, ' ', yyyy], locale: GermanDateLocale());

如果有人想将字符串格式的日期转换为其他字符串格式，首先使用DateTime.parse("2019-09-30")，然后将其传递给DateFormat("date pattern").format()

dateFormate = DateFormat("dd-MM-yyyy").format(DateTime.parse("2019-09-30"));

参考:Dart -如何将简单的日期字符串格式从yyyy-MM-dd更改为dd-MM-yyyy

/// Get date as a string for display.
String getFormattedDate(String date) {
  /// Convert into local date format.
  var localDate = DateTime.parse(date).toLocal();

  /// inputFormat - format getting from api or other func.
  /// e.g If 2021-05-27 9:34:12.781341 then format must be yyyy-MM-dd HH:mm
  /// If 27/05/2021 9:34:12.781341 then format must be dd/MM/yyyy HH:mm
  var inputFormat = DateFormat('yyyy-MM-dd HH:mm');
  var inputDate = inputFormat.parse(localDate.toString());

  /// outputFormat - convert into format you want to show.
  var outputFormat = DateFormat('dd/MM/yyyy HH:mm');
  var outputDate = outputFormat.format(inputDate);

  return outputDate.toString();
}