# eggert/tz

Time zone database and code

Repository: https://github.com/eggert/tz
Canonical: https://ross.abutalabs.com/products/tz
Homepage: https://www.iana.org/time-zones
Language: C
License: NOASSERTION
License Family: other
Last push: 2026-08-24T17:41:55+00:00

## Health v2 (maintenance only)
Score: 77/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 35, longevity 100
- inputs: {"age_days": 5159, "days_push": 9, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases, no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1826, forks 258 (observed 2026-08-28T04:05:41.322277+00:00)

## What it is
The IANA Time Zone Database (tzdb/zoneinfo) with its C reference implementation, containing historical and current local time rules, UTC offsets, and daylight-saving transitions for locations worldwide. It is periodically updated to reflect political changes to time zone boundaries and DST rules, and is the canonical source consumed by operating systems and software vendors.

## Use cases
- convert timestamps between time zones correctly
- get current UTC offset for a city
- handle daylight saving time transitions in software
- look up historical time zone changes for a location
- compile zoneinfo files for an operating system
- track upcoming DST rule changes by country

## When to choose
- you need authoritative, continuously updated time zone and DST data
- you are building an OS, runtime, or library that must resolve local times anywhere in the world
- you need historical civil time data, not just current offsets

## When to avoid
- you only need simple UTC arithmetic with no local time conversion
- you want a high-level timezone API in your language rather than raw data and C code
- you need real-time clock synchronization or NTP

## Facets
- artifact type: dataset
- maturity: active
- function: date-time, parser, developer-tools
- domain: developer-tools, operating-systems, cross-platform
- platform: cross-platform, windows, bsd, c
- tags: timezone-database, zoneinfo, tzdata, daylight-saving-time, utc-offsets, iana, localization, linux, macos

## Member repositories
- eggert/tz (main) score 77

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:41.322277+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 2026-08-30T03:19:34.219055+00:00, confidence not recorded.
  - readme: https://github.com/eggert/tz (fetched 2026-08-28T04:05:41.322277+00:00, sha 38b3f33eaddf)
  - homepage: https://www.iana.org/time-zones (fetched 2026-08-29T10:58:31.407502+00:00, sha ebf3473afb8c)
  - site_page: https://www.iana.org/about (fetched 2026-08-29T10:58:31.409820+00:00, sha dc4279548ef3)
  - site_page: https://www.iana.org/about/organization (fetched 2026-08-29T10:58:31.416762+00:00, sha e37bb6c11213)
  - site_page: https://www.iana.org/time-zones/releases/2026c (fetched 2026-08-29T10:58:31.411468+00:00, sha 85b5948402af)
  - site_page: https://www.iana.org/time-zones/releases (fetched 2026-08-29T10:58:31.413226+00:00, sha 0c894f5e0ec2)
- Data as of 2026-08-30T08:39:29.467469+00:00.