Date.now()
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.
TheDate.now() static method returns the number of milliseconds elapsed since theepoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.
Try it
// This example takes 2 seconds to runconst start = Date.now();console.log("starting timer...");// Expected output: "starting timer..."setTimeout(() => { const ms = Date.now() - start; console.log(`seconds elapsed = ${Math.floor(ms / 1000)}`); // Expected output: "seconds elapsed = 2"}, 2000);Syntax
Date.now()Parameters
None.
Return value
A number representing thetimestamp, in milliseconds, of the current time.
Description
Reduced time precision
To offer protection against timing attacks andfingerprinting, the precision ofDate.now() might get rounded depending on browser settings. In Firefox, theprivacy.reduceTimerPrecision preference is enabled by default and defaults to 2ms. You can also enableprivacy.resistFingerprinting, in which case the precision will be 100ms or the value ofprivacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.
For example, with reduced time precision, the result ofDate.now() will always be a multiple of 2, or a multiple of 100 (orprivacy.resistFingerprinting.reduceTimerPrecision.microseconds) withprivacy.resistFingerprinting enabled.
// reduced time precision (2ms) in Firefox 60Date.now();// Might be:// 1519211809934// 1519211810362// 1519211811670// …// reduced time precision with `privacy.resistFingerprinting` enabledDate.now();// Might be:// 1519129853500// 1519129858900// 1519129864400// …Examples
Measuring time elapsed
You can useDate.now() to get the current time in milliseconds, then subtract a previous time to find out how much time elapsed between the two calls.
const start = Date.now();doSomeLongRunningProcess();console.log(`Time elapsed: ${Date.now() - start} ms`);For more complex scenarios, you may want to use theperformance API instead.
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-date.now |