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()
Parameters
None.
Return value
Description
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()
const d = new Date(0); // 1970-01-01T00:00:00.000Z
console.log(d.valueOf()); // 0
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-date.prototype.valueof |