A snippet of code violating the Don't Repeat Yourself (DRY) principle and then, fixing it.

dry_demo.dart

import 'package:intl/intl.dart';

void main() {
  /// This assessment is done using the Dart Programming Language

  /// The next lines of code describes a snippet of code violating the DRY Principle
  /// DRY basically means "Don't Repeat Yourself" and it is aimed at reducing repititions in Software Engineering

  /// A snippet of code violating the DRY principle
  /// In the code below I need to format two dates [startDate] and [endDate] using a dart
  /// package [intl]

  final startDate = DateTime.now();
  final endDate = DateTime.now().add(Duration(days: 3));

  // Formating
  String startDateString = DateFormat('EEEE, MMMM dd').format(startDate);
  String endDateString = DateFormat('EEEE, MMMM dd').format(endDate);
  print(startDateString);
  print(endDateString);

  /// This code violates the DRY principle since I'm duplicating [DateFormat('EEEE, MMMM d')],
  /// It'll be worse if I need to format the date more times, I can easily make a mistake
  /// like typing DateFormat('EERR, MMMM d').format(endDate) instead of DateFormat('EEEE, MMMM d')

  /// Fixing it
  /// The next lines of code will use a method created below [fullDateFormat] to hold the date formatting
  /// Note that in a proper application, this will be added as a method to a claas ...
  /// and in this case usually named by appending Util (i.e DateUtil) with Util meaning Utility

  String startDateFixed = fullDateFormat(startDate);
  String endDateFixed = fullDateFormat(endDate);
  print(startDateFixed);
  print(endDateFixed);
}

/// We have written this method once and can now use it in multiple places
String fullDateFormat(DateTime date) => DateFormat('EEEE, MMMM dd').format(date);

/// You can test on DartPad @ https://dartpad.dev/?