The toISOString() method returns a string in simplified extended ISO format (ISO 8601), which is always 24 or 27 characters long (YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ, respectively). The timezone is always zero UTC offset, as denoted by the suffix "Z".



Return value

A string representing the given date in the ISO 8601 format according to universal time.


Using toISOString()

var today = new Date('05 October 2011 14:48 UTC');

console.log(today.toISOString()); // Returns 2011-10-05T14:48:00.000Z

The above example uses parsing of a non–standard string value that may not be correctly parsed in non–Mozilla browsers.


This method was standardized in ECMA-262 5th edition. Engines which have not been updated to support this method can work around the absence of this method using the following shim:

if (!Date.prototype.toISOString) {
  (function() {

    function pad(number) {
      if (number < 10) {
        return '0' + number;
      return number;

    Date.prototype.toISOString = function() {
      return this.getUTCFullYear() +
        '-' + pad(this.getUTCMonth() + 1) +
        '-' + pad(this.getUTCDate()) +
        'T' + pad(this.getUTCHours()) +
        ':' + pad(this.getUTCMinutes()) +
        ':' + pad(this.getUTCSeconds()) +
        '.' + (this.getUTCMilliseconds() / 1000).toFixed(3).slice(2, 5) +



Specification Status Comment
ECMAScript 5.1 (ECMA-262)
The definition of 'Date.prototype.toISOString' in that specification.
Standard Initial definition. Implemented in JavaScript 1.8.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Date.prototype.toISOString' in that specification.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'Date.prototype.toISOString' in that specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) 9 (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.