JavaScript Date

Definition and Usage

In JavaScript, a Date is an object that stores one moment in time. Internally that moment is a count of milliseconds since 1 January 1970 UTC. You create a date with new Date() for “now”, or with parts: new Date(2026, 0, 15).

The month argument is zero-based: 0 is January and 11 is December. getDate() is the day of the month (1–31). getDay() is the weekday, and that index starts at 0 for Sunday. Setters such as setDate() change the same object. toISOString() prints a UTC string for APIs.

This page teaches what a Date is. The Date Methods index and Date Properties index list every method and property guide (getFullYear(), toISOString(), constructor, and more).

JavaScript Syntax

Common ways to create and read a date:

const now = new Date();                 // this moment
const birthday = new Date(2026, 0, 15); // 15 Jan 2026, local
const year = birthday.getFullYear();    // 2026
const month = birthday.getMonth();      // 0  (January)
const stamp = Date.now();               // ms since the epoch
const utc = birthday.toISOString();     // UTC text for APIs

Core Ideas

Ideas every JavaScript Date tutorial builds on:

JavaScript Examples

Three short programs that show how Date works in a JS tutorial.

const birthday = new Date(2026, 0, 15);

console.log(birthday.getFullYear());
console.log(birthday.getMonth());
console.log(birthday.getDate());
console.log(birthday.getDay());

2026
0
15
4

const utc = new Date(Date.UTC(2026, 0, 15));

console.log(utc.getUTCFullYear());
console.log(utc.getUTCMonth());
console.log(utc.toISOString());

2026
0
2026-01-15T00:00:00.000Z

const d = new Date(2026, 0, 15);
d.setDate(20);
console.log(d.getDate());

const copy = new Date(d.getTime());
copy.setMonth(5);
console.log(d.getMonth());
console.log(copy.getMonth());

20
0
5

Next: Methods & Properties Indexes

After you know what a Date is, open the indexes for full tutorials on every essential Date API in this JavaScript series.

Full lists: Date Methods index and Date Properties index.