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IANA Tz Data

Unofficial JSON distribution of zdumped IANA timezone data.

It should be noted that a tabular text file (not JSON) is the "official" format for the IANA timezone data. The JSON data contained in this package is provided as a convenience for the development community, and is programatically generated from the corresponding text files using the JSON conversion utility provided here.


  • The data in this package is intended to serve as a common reference point for most JavaScript packages.
  • Allow i18n libraries to define IANA timezone data as versioned dependency.

What's not included

No code other than the conversion utility is included.

The official data has additional information and has a different structure than what's distributed here. The official data has Zones and Rules

What's included

A JSON representation of the timezone transitions (actually, the output of zdump -v) for every timezone ids, which is what moment-timezone, globalize, and perhaps other JavaScript library use to calculate a date in a specific timezone ids. The structure looks like the below.

  "zoneData": {
    "America": {
      "New_York": {
        abbrs: [],
        untils: [],
        offsets: [],
        isdsts: []


Latest official release is version 2019c, published on 2019-09-11.


Installation using NPM:

npm install --save iana-tz-data

We follow a semver corresponding version based on the official version. The major version corresponds to the year and the minor corresponds to the letter. The patch version is independent and used for any necessary package fixes.

Official version Our corresponding semver version
2019c 2019.2
2019b 2019.1
2018i 2018.8
2018g 2018.6
2018f 2018.5
2018e 2018.4
2018d 2018.3
2018c 2018.2
2018b 2018.1
2017c 2017.2
2017b 2017.1
2017a 2017.0

On your application, you can access IANA timezone JSON data by importing the "iana-tz-data" module.

import IANATimezoneData from "iana-tz-data";


MIT © Rafael Xavier de Souza


Unofficial JSON distribution of zdumped IANA timezone data.







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