Cookbooks
Dart
Chapter 7. Dates and Times
Comparing two dates

Dart:
Comparing two dates

How to:

In Dart, you can compare dates using the DateTime class, which offers methods like isBefore, isAfter, and isAtSameMomentAs for direct comparison. Additionally, the difference between dates can be determined using the difference() method, providing a Duration object that details the span between the two points in time.

Here’s a basic example illustrating these concepts:

void main() {
  DateTime eventStart = DateTime(2023, 5, 15);
  DateTime eventEnd = DateTime(2023, 5, 20);
  
  // Checking if one date is before another
  if (eventStart.isBefore(eventEnd)) {
    print("The event start date is before the event end date.");
  }

  // Checking if two dates are the same
  if (!eventStart.isAtSameMomentAs(eventEnd)) {
    print("The starting and ending dates are not the same.");
  }
  
  // Calculating the difference between two dates
  Duration eventDuration = eventEnd.difference(eventStart);
  print("The event lasts for ${eventDuration.inDays} days.");
}

/*
Output:
The event start date is before the event end date.
The starting and ending dates are not the same.
The event lasts for 5 days.
*/

For more advanced date manipulations, such as format conversions, you might find the DateFormat class from the intl package helpful. Below is an example demonstrating how to use it for formatting and comparing dates:

First, include the intl package in your pubspec.yaml:

dependencies:
  intl: ^0.17.0

Then, use it as follows:

import 'package:intl/intl.dart';

void main() {
  DateTime departureDate = DateTime(2023, 5, 15);
  DateTime returnDate = DateTime.parse('2023-05-20');

  // Formatting dates
  var formatter = DateFormat('yyyy-MM-dd');
  print("Departure: ${formatter.format(departureDate)}");
  print("Return: ${formatter.format(returnDate)}");

  // Compare using formatted strings
  if (formatter.format(departureDate) == formatter.format(returnDate)) {
    print("Departure and return dates are the same.");
  } else {
    print("Departure and return dates are different.");
  }
}

/*
Output:
Departure: 2023-05-15
Return: 2023-05-20
Departure and return dates are different.
*/

This example showcases how to compare two DateTime objects both directly and by using formatted strings for comparisons that need to ignore specific components like time.

Calculating a date in the future or pastConverting a date into a string