How to ISO 8601 format a Date with Timezone Offset in JavaScript?

Question

Goal: Find the local time and UTC time offset then construct the URL in following format.

Example URL: /Actions/Sleep?duration=2002-10-10T12:00:00−05:00

The format is based on the W3C recommendation. The documentation says:

For example, 2002-10-10T12:00:00−05:00 (noon on 10 October 2002, Central Daylight Savings Time as well as Eastern Standard Time in the U.S.) is equal to 2002-10-10T17:00:00Z, five hours later than 2002-10-10T12:00:00Z.

So based on my understanding, I need to find my local time by new Date() then use getTimezoneOffset() function to compute the difference then attach it to the end of string.

1. Get local time with format

   var local = new Date().format("yyyy-MM-ddThh:mm:ss"); // 2013-07-02T09:00:00
   

2. Get UTC time offset by hour

   var offset = local.getTimezoneOffset() / 60; // 7
   

3. Construct URL (time part only)

   var duration = local + "-" + offset + ":00"; // 2013-07-02T09:00:00-7:00
   

The above output means my local time is 2013/07/02 9am and difference from UTC is 7 hours (UTC is 7 hours ahead of local time)

So far it seems to work but what if getTimezoneOffset() returns negative value like -120?

I'm wondering how the format should look like in such case because I cannot figure out from W3C documentation.

Answer 1

Here's a simple helper function that will format JS dates for you.

function toIsoString(date) {
  var tzo = -date.getTimezoneOffset(),
      dif = tzo >= 0 ? '+' : '-',
      pad = function(num) {
          return (num < 10 ? '0' : '') + num;
      };

  return date.getFullYear() +
      '-' + pad(date.getMonth() + 1) +
      '-' + pad(date.getDate()) +
      'T' + pad(date.getHours()) +
      ':' + pad(date.getMinutes()) +
      ':' + pad(date.getSeconds()) +
      dif + pad(Math.floor(Math.abs(tzo) / 60)) +
      ':' + pad(Math.abs(tzo) % 60);
}

var dt = new Date();
console.log(toIsoString(dt));

Answer 2

getTimezoneOffset() returns the opposite sign of the format required by the spec that you referenced.

This format is also known as ISO8601, or more precisely as RFC3339.

In this format, UTC is represented with a Z while all other formats are represented by an offset from UTC. The meaning is the same as JavaScript's, but the order of subtraction is inverted, so the result carries the opposite sign.

Also, there is no method on the native Date object called format, so your function in #1 will fail unless you are using a library to achieve this. Refer to this documentation.

If you are seeking a library that can work with this format directly, I recommend trying moment.js. In fact, this is the default format, so you can simply do this:

var m = moment();    // get "now" as a moment
var s = m.format();  // the ISO format is the default so no parameters are needed

// sample output:   2013-07-01T17:55:13-07:00

This is a well-tested, cross-browser solution, and has many other useful features.

Answer 3

I think it is worth considering that you can get the requested info with just a single API call to the standard library...

new Date().toLocaleString( 'sv', { timeZoneName: 'short' } );

// produces "2019-10-30 15:33:47 GMT−4"

You would have to do text swapping if you want to add the 'T' delimiter, remove the 'GMT-', or append the ':00' to the end.

But then you can easily play with the other options if you want to eg. use 12h time or omit the seconds etc.

Note that I'm using Sweden as locale because it is one of the countries that uses ISO 8601 format. I think most of the ISO countries use this 'GMT-4' format for the timezone offset other then Canada which uses the time zone abbreviation eg. "EDT" for eastern-daylight-time.

You can get the same thing from the newer standard i18n function "Intl.DateTimeFormat()" but you have to tell it to include the time via the options or it will just give date.

Answer 4

My answer is a slight variation for those who just want today's date in the local timezone in the YYYY-MM-DD format.

Let me be clear:

My Goal: get today's date in the user's timezone but formatted as ISO8601 (YYYY-MM-DD)

Here is the code:

new Date().toLocaleDateString("sv") // "2020-02-23" // 

This works because the Sweden locale uses the ISO 8601 format.

Answer 5

This is my function for the clients timezone, it's lite weight and simple

  function getCurrentDateTimeMySql() {        
      var tzoffset = (new Date()).getTimezoneOffset() * 60000; //offset in milliseconds
      var localISOTime = (new Date(Date.now() - tzoffset)).toISOString().slice(0, 19).replace('T', ' ');
      var mySqlDT = localISOTime;
      return mySqlDT;
  }

Answer 6

Check this:

function dateToLocalISO(date) {
    const off    = date.getTimezoneOffset()
    const absoff = Math.abs(off)
    return (new Date(date.getTime() - off*60*1000).toISOString().substr(0,23) +
            (off > 0 ? '-' : '+') + 
            Math.floor(absoff / 60).toFixed(0).padStart(2,'0') + ':' + 
            (absoff % 60).toString().padStart(2,'0'))
}

// Test it:
d = new Date()

dateToLocalISO(d)
// ==> '2019-06-21T16:07:22.181-03:00'

// Is similar to:

moment = require('moment')
moment(d).format('YYYY-MM-DDTHH:mm:ss.SSSZ') 
// ==> '2019-06-21T16:07:22.181-03:00'

Answer 7

You can achieve this with a few simple extension methods. The following Date extension method returns just the timezone component in ISO format, then you can define another for the date/time part and combine them for a complete date-time-offset string.

Date.prototype.getISOTimezoneOffset = function () {
    const offset = this.getTimezoneOffset();
    return (offset < 0 ? "+" : "-") + Math.floor(Math.abs(offset / 60)).leftPad(2) + ":" + (Math.abs(offset % 60)).leftPad(2);
}

Date.prototype.toISOLocaleString = function () {
    return this.getFullYear() + "-" + (this.getMonth() + 1).leftPad(2) + "-" +
        this.getDate().leftPad(2) + "T" + this.getHours().leftPad(2) + ":" +
        this.getMinutes().leftPad(2) + ":" + this.getSeconds().leftPad(2) + "." +
        this.getMilliseconds().leftPad(3);
}

Number.prototype.leftPad = function (size) {
    var s = String(this);
    while (s.length < (size || 2)) {
        s = "0" + s;
    }
    return s;
}

Example usage:

var date = new Date();
console.log(date.toISOLocaleString() + date.getISOTimezoneOffset());
// Prints "2020-08-05T16:15:46.525+10:00"

I know it's 2020 and most people are probably using Moment.js by now, but a simple copy & pastable solution is still sometimes handy to have.

(The reason I split the date/time and offset methods is because I'm using an old Datejs library which already provides a flexible toString method with custom format specifiers, but just doesn't include the timezone offset. Hence, I added toISOLocaleString for anyone without said library.)

Answer 8

Just my two cents here

I was facing this issue with datetimes so what I did is this:

const moment = require('moment-timezone')

const date = moment.tz('America/Bogota').format()

Then save date to db to be able to compare it from some query.

---

To install moment-timezone

npm i moment-timezone

Answer 9

No moment.js needed: Here's a full round trip answer, from an input type of "datetime-local" which outputs an ISOLocal string to UTCseconds at GMT and back:

<input type="datetime-local" value="2020-02-16T19:30">

isoLocal="2020-02-16T19:30"
utcSeconds=new Date(isoLocal).getTime()/1000

//here you have 1581899400 for utcSeconds

let isoLocal=new Date(utcSeconds*1000-new Date().getTimezoneOffset()*60000).toISOString().substring(0,16)
2020-02-16T19:30

Answer 10

• date to ISO string,
• with local(computer) time zone,
• with or without milliseconds

ISO ref: https://en.wikipedia.org/wiki/ISO_8601

how to use: toIsoLocalTime(new Date())

function toIsoLocalTime(value) {
    if (value instanceof Date === false)
        value = new Date();    
    const off = value.getTimezoneOffset() * -1;
    const del = value.getMilliseconds() ? 'Z' : '.'; // have milliseconds ?
    value = new Date(value.getTime() + off * 60000); // add or subtract time zone
    return value
        .toISOString()
        .split(del)[0]
        + (off < 0 ? '-' : '+')
        + ('0' + Math.abs(Math.floor(off / 60))).substr(-2)
        + ':'
        + ('0' + Math.abs(off % 60)).substr(-2);
}

function test(value) {
    const event = new Date(value);
    console.info(value + ' -> ' + toIsoLocalTime(event) + ', test = ' + (event.getTime() === (new Date(toIsoLocalTime(event))).getTime() ));
}

test('2017-06-14T10:00:00+03:00'); // test with timezone
test('2017-06-14T10:00:00'); // test with local timezone
test('2017-06-14T10:00:00Z'); // test with UTC format
test('2099-12-31T23:59:59.999Z'); // date with milliseconds
test((new Date()).toString()); // now

Answer 11

Use Temporal.

Temporal.Now.zonedDateTimeISO().toString()
// '2022-08-09T14:16:47.762797591-07:00[America/Los_Angeles]'

To omit the fractional seconds and IANA time zone:

Temporal.Now.zonedDateTimeISO().toString({
  timeZoneName: "never",
  fractionalSecondDigits: 0
})
// '2022-08-09T14:18:34-07:00'

Note: Temporal is currently (2022) available as a polyfill, but will soon be available in major browsers.

Answer 12

consider using moment (like Matt's answer).

From version 2.20.0, you may call .toISOString(true) to prevent UTC conversion:

console.log(moment().toISOString(true));

// sample output:   2022-04-06T16:26:36.758+03:00

Answer 13

Here are the functions I used for this end:

function localToGMTStingTime(localTime = null) {
    var date = localTime ? new Date(localTime) : new Date();
    return new Date(date.getTime() + (date.getTimezoneOffset() * 60000)).toISOString();
};

function GMTToLocalStingTime(GMTTime = null) {
    var date = GMTTime ? new Date(GMTTime) : new Date();;
    return new Date(date.getTime() - (date.getTimezoneOffset() * 60000)).toISOString();
};

Answer 14

With luxon:

DateTime.now().toISODate() // 2022-05-23

Answer 15

let myDate = new Date(dateToBeFormatted * 1000); // depends if you have milliseconds, or seconds, then the * 1000 might be not, or required.
timeOffset = myDate.getTimezoneOffset();
myDate = new Date(myDate.getTime() - (timeOffset * 60 * 1000));

console.log(myDate.toISOString().split('T')[0]);

Inspired by https://stackoverflow.com/a/29774197/11127383, including timezone offset comment.

Answer 16

a simple way to get:

//using a sample date
let iso_str = '2022-06-11T01:51:59.618Z';
let d = new Date(iso_str);

let tz = 'America/Santiago'
let options = {
    timeZone:tz ,
    timeZoneName:'longOffset',
    year: 'numeric',
    month: 'numeric',
    day: 'numeric',
    hour: 'numeric',
    minute: 'numeric',
    second: 'numeric',
    fractionalSecondDigits: 3
}


str_locale = d.toLocaleString("sv-SE",options);
iso_str_tz = str_locale.replace(/(\d{4})-(\d{2})-(\d{2})\s+(\d{2}):(\d{2}):(\d{2}),(\d+)\s+/,'$1-$2-$3T$4:$5:$6.$7').replace('GMT−', '-' ).replace('GMT+','+')


console.log('iso_str               : ',iso_str);
console.log('str_locale            : ',str_locale);
console.log('iso_str_tz            : ',iso_str_tz);
console.log('iso_str_tz --> date   : ',new Date(iso_str_tz));
console.log('iso_str_tz --> iso_str: ',new Date(iso_str_tz).toISOString());

Answer 17

Using moment.js, you can use keepOffset parameter of toISOString:

toISOString(keepOffset?: boolean): string;

moment().toISOString(true)

Answer 18

Alternative approach with dayjs

import dayjs from "dayjs"

const formattedDateTime = dayjs(new Date()).format()

console.log(formattedDateTime) // Prints 2022-11-09T07:49:29+03:00

Answer 19

Here's another way a convert your date with an offset.

function toCustomDateString(date, offset) {
  function pad(number) {
    if (number < 10) {
      return "0" + number;
    }
    return number;
  }

  var offsetHours = offset / 60;
  var offsetMinutes = offset % 60;

  var sign = (offset > 0) ? "+" : "-";
  offsetHours = pad(Math.floor(Math.abs(offsetHours)));
  offsetMinutes = pad(Math.abs(offsetMinutes));

  return date.getFullYear() +
    "-" + pad(date.getMonth() + 1) +
    "-" + pad(date.getDate()) +
    "T" + pad(date.getHours()) +
    ":" + pad(date.getMinutes()) +
    ":" + pad(date.getSeconds()) +
    sign + offsetHours +
    ":" + offsetMinutes;
}

Then you can use it like this:

var date = new Date();
var offset = 330; // offset in minutes from UTC, for India it is 330 minutes ahead of UTC
var customDateString = toCustomDateString(date, offset);
console.log(customDateString);
// Output: "2023-02-09T10:29:31+05:30"

Answer 20

If you are looking for an easy one-liner to get the current date in ISO format here it is.

const currentIsoDateString = new Date(Date.now() - new Date().getTimezoneOffset() * 60000).toISOString()

You can change this to get the ISO date/time string for other dates by replacing the Date.now() with your epoch date integer.

Here is how it works from the inside out. Date.now() returns the current time in milliseconds since the epoch Jan. 1st 1970. For me the current local date/time is 2023-07-05 09:57:32 (ex. 1688565167374) but Date.now does not care about the local time, it just gives the time from the epoch regardless of local time, so we need to adjust.

new Date().getTimezonOffset() returns the local timezone offset from UTC. In my case it is 240 or 4 hours. We multiply these minutes by 60000 to convert it to milliseconds and subtract the result from the UTC.

Then we can use the handy .toISOString() native function to get a nicely formatted ISO string. '2023-07-05T09:58:18.119Z'

No libraries required :-)

Answer 21

function setDate(){
    var now = new Date();
    now.setMinutes(now.getMinutes() - now.getTimezoneOffset());
    var timeToSet = now.toISOString().slice(0,16);

    /*
        If you have an element called "eventDate" like the following:

        <input type="datetime-local" name="eventdate" id="eventdate" />

        and you would like to  set the current and minimum time then use the following:
    */

    var elem = document.getElementById("eventDate");
    elem.value = timeToSet;
    elem.min = timeToSet;
}

Answer 22

I found another more easy solution:

let now = new Date();
// correct time zone offset for generating iso string
now.setMinutes(now.getMinutes() - now.getTimezoneOffset())
now = now.toISOString();

I undo the timezone offset by substracting it from the current date object. The UTC time from the date object is now pointing to the local time. That gives you the possibility to get the iso date for the local time.