There is a way to format for time zones.

console.log(new Date().toLocaleDateString('en-US', {timeZone: 'America/Denver'}))
// 11/13/2018
console.log(new Date().toLocaleTimeString('en-US', {timeZone: 'America/Denver'}))
// 2:30:54 PM
console.log(new Date().toLocaleTimeString('en-US', {timeZone: 'America/New_York'}))
// 4:31:26 PM

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleDateString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleTimeString

Answer from j4ys0n on Stack Overflow
🌐
Stack Overflow
stackoverflow.com › questions › 2613511 › javascript-dateformat-for-different-timezones
Javascript DateFormat for different timezones - Stack Overflow
Top answer
1 of 9
27

There is a way to format for time zones.

console.log(new Date().toLocaleDateString('en-US', {timeZone: 'America/Denver'}))
// 11/13/2018
console.log(new Date().toLocaleTimeString('en-US', {timeZone: 'America/Denver'}))
// 2:30:54 PM
console.log(new Date().toLocaleTimeString('en-US', {timeZone: 'America/New_York'}))
// 4:31:26 PM

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleDateString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleTimeString

2 of 9
3

The ISO Extended format for common date is YYYY-MM-DD, and for time is hh:mm:ss. Either format can be understood, unambiguously, worldwide.

See also: http://jibbering.com/faq/#dates

🌐
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Date
Date - JavaScript | MDN
In essence, the timezone offset is the offset from UTC time, at the time represented by the Date object and at the location of the host environment. There are two groups of Date methods: one group gets and sets various date components by interpreting the timestamp as a local time, while the other uses UTC. The Date() constructor can be called with two or more arguments, in which case they are interpreted as the year, month, day, hour, minute, second, and millisecond, respectively, in local time.
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MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Intl › DateTimeFormat › DateTimeFormat
Intl.DateTimeFormat() constructor - JavaScript | MDN
It expands to styles for weekday, day, month, year, and era, with the exact combination of values depending on the locale. When formatting objects such as Temporal.PlainDate, Temporal.PlainYearMonth, and Temporal.PlainMonthDay, dateStyle will resolve to only those fields relevant to the object. ... The time formatting style to use. Possible values are "full", "long", "medium", and "short". It expands to styles for hour, minute, second, and timeZoneName, with the exact combination of values depending on the locale.
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Twilio
twilio.com › en-us › blog › developers › tutorials › building-blocks › converting-formatting-dates-timezones-javascript
Converting and Formatting Dates and Time Zones with JavaScript | Twilio
June 13, 2025 - Learn to use the Internationalization API to convert and formate dates across time zones in JavaScript.
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30 Seconds of Code
30secondsofcode.org › home › javascript › date › date to iso format with timezone
Format a date to ISO string with timezone using JavaScript - 30 seconds of code
January 7, 2024 - JavaScript's built-in Date.prototype.toISOString() method converts a date to ISO string in UTC time. const toISOString = date => date.toISOString(); toISOString( new Date('2024-01-06T19:20:34+02:00') ); // '2024-01-06T17:20:34.000Z' In order ...
🌐
W3Schools
w3schools.com › js › js_date_formats.asp
JavaScript Date Formats
The ISO 8601 syntax (YYYY-MM-DD) is also the preferred JavaScript date format: const d = new Date("2015-03-25"); Try it Yourself » · The computed date will be relative to your time zone.
🌐
DEV Community
dev.to › dhrn › time-zones-and-date-formats-in-javascript-1mpe
🌍 Time Zones and Date Formats in JavaScript - DEV Community
February 21, 2023 - The Intl.DateTimeFormat constructor provides a way to create localized date and time strings, including the time zone. const date = new Date(); const options = { dateStyle: 'full', timeStyle: 'long' }; const formatter = new Intl.DateTimeFor...
🌐
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Date › toISOString
Date.prototype.toISOString() - JavaScript | MDN
The toISOString() method of Date ... on 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 UTC, as denoted by the suffix Z....
Find elsewhere
🌐
GeeksforGeeks
geeksforgeeks.org › javascript › how-to-convert-date-to-another-timezone-in-javascript
How to Convert Date to Another Timezone in JavaScript? - GeeksforGeeks
July 12, 2025 - This ensures that the displayed time aligns with the selected timezone, often using built-in methods or external libraries. Intl.DateTimeFormat() in JavaScript allows formatting dates according to a specific locale and timezone.
🌐
Bobby Hadz
bobbyhadz.com › blog › javascript-initialize-date-with-timezone
How to initialize JavaScript Date to a Particular Time Zone | bobbyhadz
For this reason, it's best to use the toLocaleString method to get a string that represents the time zone and use the options object parameter to format the string according to your needs.
🌐
CoreUI
coreui.io › blog › how-to-manage-date-and-time-in-specific-timezones-using-javascript
How to Manage Date and Time in Specific Timezones Using JavaScript · CoreUI
January 22, 2025 - Effectively handling dates and times in specific timezones requires a mix of native JavaScript capabilities and third-party libraries. Here are the key strategies: Use the Intl.DateTimeFormat API for formatting in specific timezones. Calculate ...
🌐
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Date › toLocaleDateString
Date.prototype.toLocaleDateString() - JavaScript | MDN
Dezember 2012 console.log(event.toLocaleDateString("ar-EG", options)); // Expected output (varies according to local timezone): الخميس، ٢٠ ديسمبر، ٢٠١٢ console.log(event.toLocaleDateString(undefined, options)); // Expected output (varies according to local timezone and default locale): Thursday, December 20, 2012 ... The locales and options parameters customize the behavior of the function and let applications specify the language whose formatting conventions should be used. In implementations that support the Intl.DateTimeFormat API, these parameters correspond exactly to the Intl.DateTimeFormat() constructor's parameters. Implementations without Intl.DateTimeFormat support are asked to ignore both parameters, making the locale used and the form of the string returned entirely implementation-dependent.
🌐
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Intl › DateTimeFormat
Intl.DateTimeFormat - JavaScript | MDN
The used calendar and numbering formats can also be set independently via options arguments: ... const options = { calendar: "chinese", numberingSystem: "arab" }; const dateFormat = new Intl.DateTimeFormat(undefined, options); const usedOptions = dateFormat.resolvedOptions(); console.log(usedOptions.calendar); // "chinese" console.log(usedOptions.numberingSystem); // "arab" console.log(usedOptions.timeZone); // "America/New_York" (the users default timezone)
🌐
Full Stack Foundations
fullstackfoundations.com › blog › javascript date tutorial: get the timezone right!
JavaScript Date Tutorial: Get the Timezone Right!
March 29, 2024 - We’ll talk a little more about this format later, but for now, just remember that the T is the indicator for time, while the Z is the indicator of timezone. In this case, “Z” comes from “Zulu Time”, which is a military time zone reference for the UTC timezone. So remember: Z === “Zulu Time” (military) === UTC time (JavaScript) Every time you use the toISOString() on a JavaScript Date object, you will ALWAYS get a UTC representation of the date, indicated by Z.
🌐
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Date › toLocaleTimeString
Date.prototype.toLocaleTimeString() - JavaScript | MDN
const date = new Date(Date.UTC(2012, 11, 20, 3, 0, 0)); // An application may want to use UTC and make that visible const options = { timeZone: "UTC", timeZoneName: "short" }; console.log(date.toLocaleTimeString("en-US", options)); // "3:00:00 AM GMT" // Sometimes even the US needs 24-hour ...
🌐
Ursahealth
ursahealth.com › new-insights › dates-and-timezones-in-javascript
Working with dates and timezones in JavaScript: a survival guide
May 4, 2021 - > new Date("2020-01-08T19:47:00.000Z") Wed Jan 08 2020 14:47:00 GMT-0500 (Eastern Standard Time) > moment("2020-01-08T19:47:00.000Z").format("h:mm a MMM DD, YYYY") // using moment.js "2:47 pm Jan 08, 2020" > format(parseISO("2020-01-08T19:4...
🌐
Stack Overflow
stackoverflow.com › questions › 439630 › create-a-date-with-a-set-timezone-without-using-a-string-representation
javascript - Create a Date with a set timezone without using a string representation - Stack Overflow
Top answer
1 of 16
568

using .setUTCHours() it would be possible to actually set dates in UTC-time, which would allow you to use UTC-times throughout the system.

You cannot set it using UTC in the constructor though, unless you specify a date-string.

Using new Date(Date.UTC(year, month, day, hour, minute, second)) you can create a Date-object from a specific UTC time.

2 of 16
298

Simply Set the Time Zone and Get Back According

new Date().toLocaleString("en-US", {timeZone: "America/New_York"})

Other Time-zones are as Following

var world_timezones =
[
    'Europe/Andorra',
    'Asia/Dubai',
    'Asia/Kabul',
    'Europe/Tirane',
    'Asia/Yerevan',
    'Antarctica/Casey',
    'Antarctica/Davis',
    'Antarctica/DumontDUrville', 
    'Antarctica/Mawson',
    'Antarctica/Palmer',
    'Antarctica/Rothera',
    'Antarctica/Syowa',
    'Antarctica/Troll',
    'Antarctica/Vostok',
    'America/Argentina/Buenos_Aires',
    'America/Argentina/Cordoba',
    'America/Argentina/Salta',
    'America/Argentina/Jujuy',
    'America/Argentina/Tucuman',
    'America/Argentina/Catamarca',
    'America/Argentina/La_Rioja',
    'America/Argentina/San_Juan',
    'America/Argentina/Mendoza',
    'America/Argentina/San_Luis',
    'America/Argentina/Rio_Gallegos',
    'America/Argentina/Ushuaia',
    'Pacific/Pago_Pago',
    'Europe/Vienna',
    'Australia/Lord_Howe',
    'Antarctica/Macquarie',
    'Australia/Hobart',
    'Australia/Currie',
    'Australia/Melbourne',
    'Australia/Sydney',
    'Australia/Broken_Hill',
    'Australia/Brisbane',
    'Australia/Lindeman',
    'Australia/Adelaide',
    'Australia/Darwin',
    'Australia/Perth',
    'Australia/Eucla',
    'Asia/Baku',
    'America/Barbados',
    'Asia/Dhaka',
    'Europe/Brussels',
    'Europe/Sofia',
    'Atlantic/Bermuda',
    'Asia/Brunei',
    'America/La_Paz',
    'America/Noronha',
    'America/Belem',
    'America/Fortaleza',
    'America/Recife',
    'America/Araguaina',
    'America/Maceio',
    'America/Bahia',
    'America/Sao_Paulo',
    'America/Campo_Grande',
    'America/Cuiaba',
    'America/Santarem',
    'America/Porto_Velho',
    'America/Boa_Vista',
    'America/Manaus',
    'America/Eirunepe',
    'America/Rio_Branco',
    'America/Nassau',
    'Asia/Thimphu',
    'Europe/Minsk',
    'America/Belize',
    'America/St_Johns',
    'America/Halifax',
    'America/Glace_Bay',
    'America/Moncton',
    'America/Goose_Bay',
    'America/Blanc-Sablon',
    'America/Toronto',
    'America/Nipigon',
    'America/Thunder_Bay',
    'America/Iqaluit',
    'America/Pangnirtung',
    'America/Atikokan',
    'America/Winnipeg',
    'America/Rainy_River',
    'America/Resolute',
    'America/Rankin_Inlet',
    'America/Regina',
    'America/Swift_Current',
    'America/Edmonton',
    'America/Cambridge_Bay',
    'America/Yellowknife',
    'America/Inuvik',
    'America/Creston',
    'America/Dawson_Creek',
    'America/Fort_Nelson',
    'America/Vancouver',
    'America/Whitehorse',
    'America/Dawson',
    'Indian/Cocos',
    'Europe/Zurich',
    'Africa/Abidjan',
    'Pacific/Rarotonga',
    'America/Santiago',
    'America/Punta_Arenas',
    'Pacific/Easter',
    'Asia/Shanghai',
    'Asia/Urumqi',
    'America/Bogota',
    'America/Costa_Rica',
    'America/Havana',
    'Atlantic/Cape_Verde',
    'America/Curacao',
    'Indian/Christmas',
    'Asia/Nicosia',
    'Asia/Famagusta',
    'Europe/Prague',
    'Europe/Berlin',
    'Europe/Copenhagen',
    'America/Santo_Domingo',
    'Africa/Algiers',
    'America/Guayaquil',
    'Pacific/Galapagos',
    'Europe/Tallinn',
    'Africa/Cairo',
    'Africa/El_Aaiun',
    'Europe/Madrid',
    'Africa/Ceuta',
    'Atlantic/Canary',
    'Europe/Helsinki',
    'Pacific/Fiji',
    'Atlantic/Stanley',
    'Pacific/Chuuk',
    'Pacific/Pohnpei',
    'Pacific/Kosrae',
    'Atlantic/Faroe',
    'Europe/Paris',
    'Europe/London',
    'Asia/Tbilisi',
    'America/Cayenne',
    'Africa/Accra',
    'Europe/Gibraltar',
    'America/Godthab',
    'America/Danmarkshavn',
    'America/Scoresbysund',
    'America/Thule',
    'Europe/Athens',
    'Atlantic/South_Georgia',
    'America/Guatemala',
    'Pacific/Guam',
    'Africa/Bissau',
    'America/Guyana',
    'Asia/Hong_Kong',
    'America/Tegucigalpa',
    'America/Port-au-Prince',
    'Europe/Budapest',
    'Asia/Jakarta',
    'Asia/Pontianak',
    'Asia/Makassar',
    'Asia/Jayapura',
    'Europe/Dublin',
    'Asia/Jerusalem',
    'Asia/Kolkata',
    'Indian/Chagos',
    'Asia/Baghdad',
    'Asia/Tehran',
    'Atlantic/Reykjavik',
    'Europe/Rome',
    'America/Jamaica',
    'Asia/Amman',
    'Asia/Tokyo',
    'Africa/Nairobi',
    'Asia/Bishkek',
    'Pacific/Tarawa',
    'Pacific/Enderbury',
    'Pacific/Kiritimati',
    'Asia/Pyongyang',
    'Asia/Seoul',
    'Asia/Almaty',
    'Asia/Qyzylorda',
    'Asia/Qostanay', 
    'Asia/Aqtobe',
    'Asia/Aqtau',
    'Asia/Atyrau',
    'Asia/Oral',
    'Asia/Beirut',
    'Asia/Colombo',
    'Africa/Monrovia',
    'Europe/Vilnius',
    'Europe/Luxembourg',
    'Europe/Riga',
    'Africa/Tripoli',
    'Africa/Casablanca',
    'Europe/Monaco',
    'Europe/Chisinau',
    'Pacific/Majuro',
    'Pacific/Kwajalein',
    'Asia/Yangon',
    'Asia/Ulaanbaatar',
    'Asia/Hovd',
    'Asia/Choibalsan',
    'Asia/Macau',
    'America/Martinique',
    'Europe/Malta',
    'Indian/Mauritius',
    'Indian/Maldives',
    'America/Mexico_City',
    'America/Cancun',
    'America/Merida',
    'America/Monterrey',
    'America/Matamoros',
    'America/Mazatlan',
    'America/Chihuahua',
    'America/Ojinaga',
    'America/Hermosillo',
    'America/Tijuana',
    'America/Bahia_Banderas',
    'Asia/Kuala_Lumpur',
    'Asia/Kuching',
    'Africa/Maputo',
    'Africa/Windhoek',
    'Pacific/Noumea',
    'Pacific/Norfolk',
    'Africa/Lagos',
    'America/Managua',
    'Europe/Amsterdam',
    'Europe/Oslo',
    'Asia/Kathmandu',
    'Pacific/Nauru',
    'Pacific/Niue',
    'Pacific/Auckland',
    'Pacific/Chatham',
    'America/Panama',
    'America/Lima',
    'Pacific/Tahiti',
    'Pacific/Marquesas',
    'Pacific/Gambier',
    'Pacific/Port_Moresby',
    'Pacific/Bougainville',
    'Asia/Manila',
    'Asia/Karachi',
    'Europe/Warsaw',
    'America/Miquelon',
    'Pacific/Pitcairn',
    'America/Puerto_Rico',
    'Asia/Gaza',
    'Asia/Hebron',
    'Europe/Lisbon',
    'Atlantic/Madeira',
    'Atlantic/Azores',
    'Pacific/Palau',
    'America/Asuncion',
    'Asia/Qatar',
    'Indian/Reunion',
    'Europe/Bucharest',
    'Europe/Belgrade',
    'Europe/Kaliningrad',
    'Europe/Moscow',
    'Europe/Simferopol',
    'Europe/Kirov',
    'Europe/Astrakhan',
    'Europe/Volgograd',
    'Europe/Saratov',
    'Europe/Ulyanovsk',
    'Europe/Samara',
    'Asia/Yekaterinburg',
    'Asia/Omsk',
    'Asia/Novosibirsk',
    'Asia/Barnaul',
    'Asia/Tomsk',
    'Asia/Novokuznetsk',
    'Asia/Krasnoyarsk',
    'Asia/Irkutsk',
    'Asia/Chita',
    'Asia/Yakutsk',
    'Asia/Khandyga',
    'Asia/Vladivostok',
    'Asia/Ust-Nera',
    'Asia/Magadan',
    'Asia/Sakhalin',
    'Asia/Srednekolymsk',
    'Asia/Kamchatka',
    'Asia/Anadyr',
    'Asia/Riyadh',
    'Pacific/Guadalcanal',
    'Indian/Mahe',
    'Africa/Khartoum',
    'Europe/Stockholm',
    'Asia/Singapore',
    'America/Paramaribo',
    'Africa/Juba',
    'Africa/Sao_Tome',
    'America/El_Salvador',
    'Asia/Damascus',
    'America/Grand_Turk',
    'Africa/Ndjamena',
    'Indian/Kerguelen',
    'Asia/Bangkok',
    'Asia/Dushanbe',
    'Pacific/Fakaofo',
    'Asia/Dili',
    'Asia/Ashgabat',
    'Africa/Tunis',
    'Pacific/Tongatapu',
    'Europe/Istanbul',
    'America/Port_of_Spain',
    'Pacific/Funafuti',
    'Asia/Taipei',
    'Europe/Kiev',
    'Europe/Uzhgorod',
    'Europe/Zaporozhye',
    'Pacific/Wake',
    'America/New_York',
    'America/Detroit',
    'America/Kentucky/Louisville',
    'America/Kentucky/Monticello',
    'America/Indiana/Indianapolis',
    'America/Indiana/Vincennes',
    'America/Indiana/Winamac',
    'America/Indiana/Marengo',
    'America/Indiana/Petersburg',
    'America/Indiana/Vevay',
    'America/Chicago',
    'America/Indiana/Tell_City',
    'America/Indiana/Knox',
    'America/Menominee',
    'America/North_Dakota/Center',
    'America/North_Dakota/New_Salem',
    'America/North_Dakota/Beulah',
    'America/Denver',
    'America/Boise',
    'America/Phoenix',
    'America/Los_Angeles',
    'America/Anchorage',
    'America/Juneau',
    'America/Sitka',
    'America/Metlakatla',
    'America/Yakutat',
    'America/Nome',
    'America/Adak',
    'Pacific/Honolulu',
    'America/Montevideo',
    'Asia/Samarkand',
    'Asia/Tashkent',
    'America/Caracas',
    'Asia/Ho_Chi_Minh',
    'Pacific/Efate',
    'Pacific/Wallis',
    'Pacific/Apia',
    'Africa/Johannesburg'
];
🌐
Stack Overflow
stackoverflow.com › questions › 10087819 › convert-date-to-another-timezone-in-javascript
Convert date to another timezone in JavaScript - Stack Overflow
Top answer
1 of 16
469

Here is the one-liner:

function convertTZ(date, tzString) {
    return new Date((typeof date === "string" ? new Date(date) : date).toLocaleString("en-US", {timeZone: tzString}));   
}

// usage: Asia/Jakarta is GMT+7
convertTZ("2012/04/20 10:10:30 +0000", "Asia/Jakarta") // Tue Apr 20 2012 17:10:30 GMT+0700 (Western Indonesia Time)

// Resulting value is regular Date() object
const convertedDate = convertTZ("2012/04/20 10:10:30 +0000", "Asia/Jakarta") 
convertedDate.getHours(); // 17

// Bonus: You can also put Date object to first arg
const date = new Date()
convertTZ(date, "Asia/Jakarta") // current date-time in jakarta.

This is the MDN Reference.

Beware the caveat: function above works by relying on parsing toLocaleString result, which is string of a date formatted in en-US locale , e.g. "4/20/2012, 5:10:30 PM". Each browser may not accept en-US formatted date string to its Date constructor and it may return unexpected result (it may ignore daylight saving).

Currently all modern browser accept this format and calculates daylight saving correctly, it may not work on older browser and/or exotic browser.

side-note: It would be great if modern browser have toLocaleDate function, so we don't have to use this hacky work around.

2 of 16
160

Most browsers support the toLocaleString function with arguments, older browsers usually ignore the arguments.

const str = new Date().toLocaleString('en-US', { timeZone: 'Asia/Jakarta' });
console.log(str);

🌐
Stack Overflow
stackoverflow.com › questions › 15141762 › how-to-initialize-a-javascript-date-to-a-particular-time-zone
timezone - How to initialize a JavaScript Date to a particular time zone - Stack Overflow
Top answer
1 of 16
969

Background

JavaScript's Date object tracks time in UTC internally, but typically accepts input and produces output in the local time of the computer it's running on. It has very few facilities for working with time in other time zones.

The internal representation of a Date object is a single number - namely timestamp - representing the number of milliseconds that have elapsed since 1970-01-01 00:00:00 UTC, without regard to leap seconds.

There is no time zone or string format stored in the Date object itself.

When various functions of the Date object are used, the computer's local time zone is applied to the internal representation. If the function produces a string, then the computer's locale information may be taken into consideration to determine how to produce that string. The details vary per function, and some are implementation-specific.

The only operations the Date object can do with non-local time zones are:

  • It can parse a string containing a numeric UTC offset from any time zone. It uses this to adjust the value being parsed, and stores the UTC equivalent. The original local time and offset are not retained in the resulting Date object. For example:

      var d = new Date("2020-04-13T00:00:00.000+08:00");
  d.toISOString()  //=> "2020-04-12T16:00:00.000Z"
  d.valueOf()      //=> 1586707200000  (this is what is actually stored in the object)

  • In environments that have implemented the ECMASCript Internationalization API (aka "Intl"), a Date object can produce a locale-specific string adjusted to a given time zone identifier. This is accomplished via the timeZone option to toLocaleString and its variations. Most implementations will support IANA time zone identifiers, such as 'America/New_York'. For example:

      var d = new Date("2020-04-13T00:00:00.000+08:00");
  d.toLocaleString('en-US', { timeZone: 'America/New_York' })
  //=> "4/12/2020, 12:00:00 PM"
  // (midnight in China on April 13th is noon in New York on April 12th)

    Most modern environments support the full set of IANA time zone identifiers (see the compatibility table here). However, keep in mind that the only identifier required to be supported by Intl is 'UTC', thus you should check carefully if you need to support older browsers or atypical environments (for example, lightweight IoT devices).

Libraries

There are several libraries that can be used to work with time zones. Though they still cannot make the Date object behave any differently, they typically implement the standard IANA timezone database and provide functions for using it in JavaScript. Modern libraries use the time zone data supplied by the Intl API, but older libraries typically have overhead, especially if you are running in a web browser, as the database can get a bit large. Some of these libraries also allow you to selectively reduce the data set, either by which time zones are supported and/or by the range of dates you can work with.

Here are the libraries to consider:

Intl-based Libraries

New development should choose from one of these implementations, which rely on the Intl API for their time zone data:

  • Luxon (successor of Moment.js)
  • date-fns-tz (extension for date-fns)
  • Day.js (when using its Timezone plugin)

Non-Intl Libraries

These libraries are maintained, but carry the burden of packaging their own time zone data, which can be quite large.

  • js-joda/timezone (extension for js-joda)
  • moment-timezone* (extension for Moment.js)
  • date-fns-timezone (extension for older 1.x of date-fns)
  • BigEasy/TimeZone
  • tz.js

* While Moment and Moment-Timezone were previously recommended, the Moment team now prefers users chose Luxon for new development.

Discontinued Libraries

These libraries have been officially discontinued and should no longer be used.

  • WallTime-js
  • TimeZoneJS

Future Proposals

The TC39 Temporal Proposal aims to provide a new set of standard objects for working with dates and times in the JavaScript language itself. This will include support for a time zone aware object.

Common Errors

There are several approaches that are often tried, which are in error and should usually be avoided.

Re-Parsing

new Date(new Date().toLocaleString('en', {timeZone: 'America/New_York'}))

The above approach correctly uses the Intl API to create a string in a specific time zone, but then it incorrectly passes that string back into the Date constructor. In this case, parsing will be implementation-specific, and may fail entirely. If successful, it is likely that the resulting Date object now represents the wrong instant in time, as the computer's local time zone would be applied during parsing.

Epoch Shifting

var d = new Date();
d.setTime(d.getTime() + someOffset * 60000);

The above approach attempts to manipulate the Date object's time zone by shifting the Unix timestamp by some other time zone offset. However, since the Date object only tracks time in UTC, it actually just makes the Date object represent a different point in time.

The same approach is sometimes used directly on the constructor, and is also invalid.

Epoch Shifting is sometimes used internally in date libraries as a shortcut to avoid writing calendar arithmetic. When doing so, any access to non-UTC properties must be avoided. For example, once shifted, a call to getUTCHours would be acceptable, but a call to getHours would be invalid because it uses the local time zone.

It is called "epoch shifting", because when used correctly, the Unix Epoch (1970-01-01T00:00:00.000Z) is now no longer correlated to a timestamp of 0 but has shifted to a different timestamp by the amount of the offset.

If you're not authoring a date library, you should not be epoch shifting.

For more details about epoch shifting, watch this video clip from Greg Miller at CppCon 2015. The video is about time_t in C++, but the explanation and problems are identical. (For JavaScript folks, every time you hear Greg mention time_t, just think "Date object".)

Trying to make a "UTC Date"

var d = new Date();
var utcDate = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), d.getUTCDate(), d.getUTCHours(), d.getUTCMinutes(), d.getUTCSeconds(), d.getUTCMilliseconds()));

In this example, both d and utcDate are identical. The work to construct utcDate was redundant, because d is already in terms of UTC. Examining the output of toISOString, getTime, or valueOf functions will show identical values for both variables.

A similar approach seen is:

var d = new Date();
var utcDate = new Date(d.getUTCFullYear(), d.getUTCMonth(), d.getUTCDate(), d.getUTCHours(), d.getUTCMinutes(), d.getUTCSeconds(), d.getUTCMilliseconds());

This is approach passes UTC values into the Date constructor where local time values are expected. The resulting Date object now represents a completely different point in time. It is essentially the same result as epoch shifting described earlier, and thus should be avoided.

The correct way to get a UTC-based Date object is simply new Date(). If you need a string representation that is in UTC, then use new Date().toISOString().

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As Matt Johnson said

If you can limit your usage to modern web browsers, you can now do the following without any special libraries:

new Date().toLocaleString("en-US", {timeZone: "America/New_York"})

This isn't a comprehensive solution, but it works for many scenarios that require only output conversion (from UTC or local time to a specific time zone, but not the other direction).

So although the browser can not read IANA timezones when creating a date, or has any methods to change the timezones on an existing Date object, there seems to be a hack around it.

Consider the following function

function changeTimezone(date, ianatz) {

  // suppose the date is 12:00 UTC
  var invdate = new Date(date.toLocaleString('en-US', {
    timeZone: ianatz
  }));

  // then invdate will be 07:00 in Toronto
  // and the diff is 5 hours
  var diff = date.getTime() - invdate.getTime();

  // so 12:00 in Toronto is 17:00 UTC
  return new Date(date.getTime() - diff); // needs to substract

}

However, closely looking at the return value, this can be simplified to:

function changeTimezone(date, ianatz) {
  return new Date(date.toLocaleString('en-US', {
    timeZone: ianatz
  }));
}

// E.g.
var here = new Date();
var there = changeTimezone(here, "America/Toronto");

console.log(`Here: ${here.toString()}\nToronto: ${there.toString()}`);

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dev.to › ayako_yk › javascript-date-objects-basics-and-time-zone-adjustments-4g14
JavaScript Date Objects: Basics and Time Zone Adjustments - DEV Community
February 16, 2025 - A JavaScript date is fundamentally specified as the time in milliseconds that has elapsed since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC (equivalent to the UNIX epoch).