date-fns

Overview

date-fns is a modular JavaScript library designed for working with dates and times. Established in 2014, it provides a collection of functions for common date operations such as formatting, validation, manipulation, and calculation. Unlike some other libraries, date-fns operates directly on native JavaScript Date objects, avoiding the overhead of custom wrapper objects. This design choice aligns with modern JavaScript practices and contributes to its performance characteristics.

The library is built with a functional programming paradigm, meaning its functions are pure and immutable. Each function takes a date and returns a new date or value, rather than modifying the original date object in place. This immutability supports predictable behavior and simplifies debugging, particularly in complex applications. date-fns also emphasizes tree-shaking, a build optimization technique that allows bundlers to remove unused code. This modularity means developers only include the specific date functions they need in their final application bundle, leading to smaller file sizes and faster load times, a critical consideration for web performance.

Targeting modern JavaScript environments, date-fns offers full TypeScript support, providing type definitions for all its functions. This enhances developer experience by enabling static type checking and improved autocompletion in IDEs. The library is also designed with internationalization (i18n) in mind, offering locale support that allows dates to be formatted according to various cultural conventions, including different date and time formats, day names, and month names. This makes it suitable for global applications requiring localized date displays. Its comprehensive documentation and examples further support developers in integrating date-fns into a wide range of projects, from single-page applications to server-side Node.js environments.

The design principles of date-fns focus on reliability and consistency. It aims to provide a robust and well-tested set of utilities that address the complexities of date handling, such as time zones, daylight saving time, and leap years. By adhering to a clear API and leveraging native browser functionality, date-fns positions itself as a dependable choice for developers seeking a lightweight yet powerful date utility solution in their JavaScript and TypeScript projects.

Key features

• Modular Architecture: Each function is an independent module, allowing for selective imports and effective tree-shaking to minimize bundle sizes.
• Native Date Object Usage: Operates directly on standard JavaScript Date objects, avoiding custom wrapper classes and potential interoperability issues.
• Immutable API: All functions are pure and do not modify the original date objects, promoting predictable state management and easier debugging.
• Comprehensive Function Set: Provides over 200 functions for parsing, formatting, validating, manipulating, and comparing dates and times.
• TypeScript Support: Includes full TypeScript definitions for type safety and improved developer experience in TypeScript projects.
• Internationalization (i18n): Offers robust locale support for formatting dates according to various cultural and language-specific conventions.
• Functional Programming Paradigm: Designed with a functional approach, making it compatible with modern JavaScript patterns and libraries.
• ES Modules (ESM) First: Primarily distributed as ES Modules, facilitating modern import syntax and efficient bundler integration.

Pricing

date-fns is distributed under the MIT License, making it a free and open-source library. There are no licensing fees, subscription costs, or premium tiers associated with its use.

For detailed licensing information, refer to the MIT License documentation.

Common integrations

• React/Vue/Angular: date-fns functions can be directly integrated into component logic for displaying and manipulating dates in UI frameworks.
• Node.js Backend Services: Used for server-side date validation, data processing, and API response formatting.
• Build Tools (Webpack, Rollup, Parcel): Its modular design allows efficient tree-shaking when bundled with tools like Parcel, reducing final application size.
• Testing Frameworks (Jest, Mocha): Simplifies testing of date-related logic by providing consistent and predictable date manipulation.
• Date Pickers & UI Components: Often used as the underlying date manipulation engine for custom or third-party date picker components.

Alternatives

• Moment.js: A long-standing and widely used JavaScript date library, known for its mutable API and wrapper objects.
• Luxon: A modern date and time library by the Moment.js team, focusing on immutability and native Intl API.
• Day.js: A minimalist date library that parses, validates, manipulates, and displays dates, designed to be a lightweight alternative with a Moment.js-like API.

Getting started

To begin using date-fns, install it via npm or yarn. This example demonstrates how to format a date, add days, and calculate the difference between two dates.

# Using npm
npm install date-fns

# Using yarn
yarn add date-fns

// Import specific functions from date-fns
import { format, addDays, differenceInDays } from 'date-fns';

// Get the current date
const today = new Date();
console.log('Today:', format(today, 'yyyy-MM-dd'));
// Example output: Today: 2026-06-09

// Add 7 days to the current date
const sevenDaysLater = addDays(today, 7);
console.log('Seven days later:', format(sevenDaysLater, 'PPPP'));
// Example output: Seven days later: Tuesday, June 16th, 2026

// Define another date
const anotherDate = new Date(2026, 5, 1); // June 1, 2026 (month is 0-indexed)
console.log('Another date:', format(anotherDate, 'yyyy/MM/dd'));
// Example output: Another date: 2026/06/01

// Calculate the difference in days between two dates
const daysDifference = differenceInDays(today, anotherDate);
console.log(`Difference between today and June 1st, 2026: ${daysDifference} days`);
// Example output: Difference between today and June 1st, 2026: 8 days

// Example with internationalization (requires importing a locale)
import { enUS, es } from 'date-fns/locale';

console.log('Today (English):', format(today, 'PPPP', { locale: enUS }));
// Example output: Today (English): Tuesday, June 9th, 2026

console.log('Today (Spanish):', format(today, 'PPPP', { locale: es }));
// Example output: Today (Spanish): martes, 9 de junio de 2026

This example demonstrates the modular import of functions like format, addDays, and differenceInDays, along with basic usage and an illustration of locale support. For a comprehensive list of available functions and their usage, refer to the date-fns documentation.