JavaScript How to Convert Timestamp to Date Easily

Use new Date(timestamp) to convert a timestamp (milliseconds since Jan 1, 1970) into a JavaScript Date object, then use methods like toLocaleString() to get a readable date.

Examples

Input0

OutputThu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)

Input1672531200000

OutputSun Jan 01 2023 00:00:00 GMT+0000 (Coordinated Universal Time)

Input-86400000

OutputTue Dec 30 1969 00:00:00 GMT+0000 (Coordinated Universal Time)

How to Think About It

To convert a timestamp to a date, think of the timestamp as the number of milliseconds passed since January 1, 1970. You create a Date object using this number, and then you can display it in a human-friendly format using built-in Date methods.

Algorithm

1

Get the timestamp value (milliseconds since Jan 1, 1970).

2

Create a new Date object using the timestamp.

3

Use Date methods like toLocaleString() to convert the Date object to a readable string.

4

Return or print the formatted date string.

Code

javascript

const timestamp = 1672531200000;
const date = new Date(timestamp);
console.log(date.toLocaleString());

Output

1/1/2023, 12:00:00 AM

Dry Run

Let's trace the timestamp 1672531200000 through the code

1

Create Date object

new Date(1672531200000) creates a Date representing Jan 1, 2023

2

Convert to string

date.toLocaleString() returns '1/1/2023, 12:00:00 AM' (format depends on locale)

Step	Value
Timestamp	1672531200000
Date object	Sun Jan 01 2023 00:00:00 GMT+0000
Formatted string	1/1/2023, 12:00:00 AM

Why This Works

Step 1: Timestamp as milliseconds

The timestamp is the number of milliseconds since January 1, 1970, which is the standard epoch time in JavaScript.

Step 2: Date object creation

Using new Date(timestamp) creates a Date object representing that exact moment in time.

Step 3: Formatting date

Calling toLocaleString() on the Date object converts it into a readable string based on your computer's locale settings.

Alternative Approaches

Using Date.UTC and manual conversion

javascript

const timestamp = 1672531200000;
const date = new Date();
date.setTime(timestamp);
console.log(date.toString());

This method sets the time of an existing Date object; it's less direct but useful if you want to reuse a Date instance.

Using Intl.DateTimeFormat for custom formatting

javascript

const timestamp = 1672531200000;
const date = new Date(timestamp);
const formatter = new Intl.DateTimeFormat('en-US', { dateStyle: 'full', timeStyle: 'long' });
console.log(formatter.format(date));

This approach gives more control over the date format but requires more code.

Complexity: O(1) time, O(1) space

Time Complexity

Creating a Date object and formatting it takes constant time, as no loops or recursion are involved.

Space Complexity

Only a few variables are used, so space usage is constant.

Which Approach is Fastest?

Using new Date(timestamp) directly is the simplest and fastest way; alternatives add formatting flexibility but with minor overhead.

Approach	Time	Space	Best For
new Date(timestamp)	O(1)	O(1)	Simple conversion
Date.setTime()	O(1)	O(1)	Reusing Date objects
Intl.DateTimeFormat	O(1)	O(1)	Custom date formatting