How to Find Difference Between Two Dates in JavaScript: Methods Compared

To find the difference between two dates in JavaScript, convert both dates to milliseconds using Date.getTime() and subtract them. Then, convert the result to desired units like days or hours by dividing by the appropriate number (e.g., 1000 * 60 * 60 * 24 for days).

Quick Comparison

Here is a quick comparison of common ways to find the difference between two dates in JavaScript.

Method	How it works	Units Supported	Requires Library	Ease of Use
Using Date.getTime()	Subtract timestamps in milliseconds	Milliseconds, seconds, minutes, hours, days	No	Simple
Using Date arithmetic	Subtract Date objects directly	Milliseconds	No	Simple but less explicit
Using moment.js	Use diff() method	Multiple units with formatting	Yes	Very easy
Using date-fns	Use differenceInDays() and similar	Multiple units	Yes	Easy and modular
Using luxon	Use diff() with units	Multiple units	Yes	Modern and powerful

Key Differences

The simplest way to find the difference between two dates in JavaScript is by using the Date.getTime() method. This method returns the number of milliseconds since January 1, 1970, for a given date. By subtracting these values for two dates, you get the difference in milliseconds, which you can convert to other units like seconds, minutes, or days by dividing by the appropriate number.

Directly subtracting two Date objects also works because JavaScript converts them to their millisecond timestamps automatically. However, this approach is less explicit and can be confusing for beginners.

For more advanced needs, libraries like moment.js, date-fns, and luxon provide built-in functions to calculate differences in various units and formats. These libraries handle edge cases like daylight saving time changes and provide cleaner syntax but require adding external dependencies.

Code Comparison

Here is how to find the difference between two dates using plain JavaScript with Date.getTime():

javascript

const date1 = new Date('2024-06-01');
const date2 = new Date('2024-06-10');

// Get difference in milliseconds
const diffInMs = date2.getTime() - date1.getTime();

// Convert milliseconds to days
const diffInDays = diffInMs / (1000 * 60 * 60 * 24);

console.log(diffInDays);

Output

9

Library Equivalent

Using date-fns library, you can find the difference in days more directly:

javascript

import { differenceInDays } from 'date-fns';

const date1 = new Date('2024-06-01');
const date2 = new Date('2024-06-10');

const diffInDays = differenceInDays(date2, date1);

console.log(diffInDays);

Output

9

When to Use Which

Choose plain JavaScript with Date.getTime() when you want a simple, dependency-free solution for basic date difference calculations. It works well for straightforward tasks like finding days or hours between two dates.

Choose a library like date-fns or luxon when you need more features, better readability, or to handle complex date scenarios such as time zones, daylight saving time, or formatting differences in multiple units.

Key Takeaways

Use Date.getTime() to get milliseconds and subtract for date differences in plain JavaScript.

Convert milliseconds to desired units by dividing by the right number (e.g., 86400000 for days).

Direct subtraction of Date objects also works but is less explicit.

Libraries like date-fns simplify date difference calculations and handle edge cases.

Pick plain JavaScript for simple tasks and libraries for complex date handling.