UTC - Local DateTime Converter

date_time_converter.dart

import 'package:json_annotation/json_annotation.dart';

class UTCDateTimeConverter implements JsonConverter<DateTime, String> {
  const UTCDateTimeConverter();

  @override
  DateTime fromJson(String dateTime) {
    return DateTime.parse(dateTime).toLocal();
  }

  @override
  String toJson(DateTime dateTime) {
    return dateTime.toUtc().toString();
  }
}

user.dart

@JsonSerializable()
@UTCDateTimeConverter()
class User {
  String name;
  DateTime lastLoginDate;

  factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
  Map<String, dynamic> toJson() => _$UserToJson(this);
}