# marnusw/date-fns-tz

Complementary library for date-fns v2 adding IANA time zone support

Repository: https://github.com/marnusw/date-fns-tz
Canonical: https://ross.abutalabs.com/products/date-fns-tz
Language: JavaScript
License: MIT
License Family: permissive
Topics: date, zone-helpers, zone-formatting, iana, date-fns, timezone, time, utilities, javascript
Last push: 2024-12-31T22:43:48+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 2888, "days_push": 610, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1181, forks 111 (observed 2026-08-28T04:03:54.045325+00:00)

## What it is
A complementary library for date-fns v3 that adds IANA time zone support using the browser's Intl API, so no time zone data needs to be bundled. It provides helpers for formatting dates in arbitrary time zones, converting between zoned and UTC times, and parsing date strings from any time zone.

## Use cases
- format a date in a specific IANA time zone regardless of system time zone
- convert a local time in one time zone to an equivalent UTC Date
- parse a date string that represents time in an arbitrary time zone
- get the UTC offset in milliseconds for a given time zone
- extend date-fns format tokens with time zone tokens like z and zzzz
- display event times to users in different time zones without bundling tz data

## When to choose
- you already use date-fns and need time zone support
- you want zero bundled time zone data by relying on the Intl API
- you need to format, convert, or parse dates across IANA time zones in JavaScript

## When to avoid
- you don't use date-fns and want a standalone date/time library
- you must support very old environments without Intl API and cannot use a polyfill
- you need offline time zone database rules beyond Intl's capabilities

## Facets
- artifact type: library
- maturity: stable
- function: date-time, serialization, developer-tools
- domain: developer-tools, web-development, cross-platform
- platform: browser, cross-platform
- tags: date-fns, timezone, iana, intl-api, date-formatting, date-parsing, javascript, nodejs

## Member repositories
- marnusw/date-fns-tz (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:54.045325+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T06:25:12.408884+00:00, confidence not recorded.
  - readme: https://github.com/marnusw/date-fns-tz (fetched 2026-08-28T04:03:54.045325+00:00, sha 3406d69ee2a7)
  - registry_npm: https://registry.npmjs.org/date-fns-tz (fetched 2026-08-29T12:31:58.116876+00:00, sha c0d546cfba9f)
- Data as of 2026-08-30T08:39:29.467469+00:00.