IANA TZ Database for Backward UTC Zones

Common errors

• TypeError: tzdataBackwardUtc is not defined

  cause Attempting to access the browser global variable `tzdataBackwardUtc` in a Node.js environment.
  fix In Node.js, use `const data = require('tzdata-backward-utc');` to import the module's JSON content. The global variable is only available when the UMD bundle is loaded in a browser.

• Cannot find module 'tzdata-backward-utc'

  cause The package has not been installed, or the import path is incorrect.
  fix Ensure the package is installed using `npm install tzdata-backward-utc` and that the import statement matches the package name exactly.

• SyntaxError: Named export 'tzData' not found. The requested module 'tzdata-backward-utc' does not provide an export named 'tzData'

  cause Attempting to use a named import for a module that provides a default export (the JSON object itself) but no named exports.
  fix Use a default import instead: `import tzData from 'tzdata-backward-utc';` for ESM, or `const tzData = require('tzdata-backward-utc');` for CommonJS.

Warnings

• breaking The IANA Time Zone Database, which this package mirrors, is updated periodically to reflect changes in political time zone boundaries, UTC offsets, and daylight-saving rules. These are data changes, not API changes, but they directly affect time calculations for historical or future dates.
  Fix: Regularly update `tzdata-backward-utc` to the latest version to ensure you are using the most current time zone rules. Be aware that time zone calculations for past or future dates may change with updates.
• gotcha This package is a specific subset of the IANA TZ database, containing only old synonyms for `Etc/UTC` and `Etc/GMT`. It does not provide comprehensive time zone data for all regions globally. Using it in isolation for general time zone handling will lead to incomplete or incorrect results.
  Fix: For full IANA time zone support, combine this module with the main `tzdata` package or other regional `tzdata-*` modules, typically integrated through a library like `timezonecomplete`.
• gotcha This module lists `tzdata-etcetera` as a peer dependency. While npm 7+ handles peer dependencies automatically, older npm versions (or other package managers) might require manual installation, or incorrect installation could lead to missing data links.
  Fix: Ensure `tzdata-etcetera` is installed alongside `tzdata-backward-utc` using `npm install tzdata-backward-utc tzdata-etcetera` or ensure your package manager correctly resolves peer dependencies.

Install

• npm install tzdata-backward-utc npm
• yarn add tzdata-backward-utc yarn
• pnpm add tzdata-backward-utc pnpm

Imports

• jsonData
  wrong:

  import jsonData from 'tzdata-backward-utc';

  correct:

  const jsonData = require('tzdata-backward-utc');

  This package is primarily consumed as a JSON module via CommonJS `require()` in Node.js. While Node.js can often import JSON directly with ESM `import`, the documentation explicitly shows `require`.
• tzdataBackwardUtc
  wrong:

  const data = tzdataBackwardUtc;

  correct:

  <!-- In browser HTML --> <script src="./tzdata-backward-utc.js"></script> <script> var data = tzdataBackwardUtc; </script>

  In a browser environment, the UMD module exposes the time zone data as a global variable `tzdataBackwardUtc`. This global is not available in Node.js environments.
• tzData
  wrong:

  import { tzData } from 'tzdata-backward-utc';

  correct:

  import tzData from 'tzdata-backward-utc';

  When using ESM in Node.js (or bundlers), the JSON data is the default export. There are no named exports from this module.

Quickstart

This quickstart demonstrates how to import the `tzdata-backward-utc` JSON data in Node.js and access its content, including specific zone information and the embedded IANA TZ Database version.

const backwardUtcData = require('tzdata-backward-utc');

console.log('Loaded backward-utc timezone data (truncated):');
console.log(Object.keys(backwardUtcData).slice(0, 5).map(key => `${key}: ${JSON.stringify(backwardUtcData[key]).slice(0, 50)}...`));

// Example of accessing a specific zone, e.g., 'UTC'
const utcZoneInfo = backwardUtcData['UTC'];
if (utcZoneInfo) {
  console.log('\nInformation for UTC zone (truncated):');
  console.log(JSON.stringify(utcZoneInfo, null, 2).slice(0, 200) + '...');
} else {
  console.log('\nUTC zone information not found.');
}

// Demonstrate use of the IANA TZ Database version property (added in v1.0.46)
if (backwardUtcData.version) {
  console.log(`\nIANA TZ Database Version: ${backwardUtcData.version}`);
} else {
  console.log('\nVersion property not found (older package version).');
}