Date.prototype.valueOf()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The valueOf() method of Date instances returns the number of milliseconds for this date since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.

Try it

const date1 = new Date(Date.UTC(96, 1, 2, 3, 4, 5));

console.log(date1.valueOf());
// Expected output: 823230245000

const date2 = new Date("02 Feb 1996 03:04:05 GMT");

console.log(date2.valueOf());
// Expected output: 823230245000

Syntax

valueOf()

Return value

A number representing the timestamp, in milliseconds, of this date. Returns NaN if the date is invalid.

The valueOf() method is part of the type coercion protocol. Because Date has a [Symbol.toPrimitive]() method, that method always takes priority over valueOf() when a Date object is implicitly coerced to a number. However, Date.prototype[Symbol.toPrimitive]() still calls this.valueOf() internally.

The Date object overrides the valueOf() method of Object. Date.prototype.valueOf() returns the timestamp of the date, which is functionally equivalent to the Date.prototype.getTime() method.

Examples

Using valueOf()

js
const d = new Date(0); // 1970-01-01T00:00:00.000Z
console.log(d.valueOf()); // 0

Specifications

Specification

ECMAScript® 2027 Language Specification
# sec-date.prototype.valueof

Browser compatibility

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This page was last modified on Jul 10, 2025 by MDN contributors.

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Standard built-in objects
Date
Constructor
1. Date()
Static methods
Instance methods
Inheritance
Object/Function
Static methods
Static properties
Instance methods
Instance properties
1. __proto__
2. constructor

Date.prototype.valueOf()

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