---
name: Time Zones
slug: time-zones
type: global_patch
status: unstable
version: 0.0.666-alpha
released: "1884-10-22T00:00:00Z (disputed)"
maintainer: "nobody (nominally: whoever wrote the Rails tzinfo gem in 2006)"
dependencies:
  - "[the sun](/the-sun)"
  - "[colonialism](/colonialism)"
  - "[hubris](/hubris)"
  - "[daylight saving time](/daylight-saving-time)"
  - political_will@unstable
license: "Public Domain / International Chaos (see: India UTC+5:30)"
tags:
  - time
  - geography
  - collective_hallucination
  - do_not_touch
  - haunted
  - "this_is_fine"
---

Time Zones

What it actually is

A global agreement to disagree about what number the sky is currently displaying, implemented via 38 separate offsets, several of which are fractional and one of which (Chatham Islands, UTC+12:45) was clearly a dare.

How it works

The earth rotates. This is fine.
the sun appears to move. Everyone notices at slightly different times.
In 1884, a room full of men in hats decided to slice the planet into 24 vertical wedges, like an orange that had done something wrong.
Countries immediately started redrawing the wedges for political reasons.
This process has never stopped.

The current system runs on vibes, UTC offsets, and a IANA timezone database maintained by volunteers who are definitely okay.

"I scheduled the meeting for 3pm EST and six people showed up, across three different days. Two were in the future." — verified user report

Features

38 distinct UTC offsets (target was 24; overage attributed to nationalism)
Half-hour offsets for India, Iran, Afghanistan, and several others who simply chose violence
Negative zero (UTC+0 vs UTC-0) which is philosophically load-bearing
daylight saving time integration, which doubles as a bug injection system twice per year
Full support for time zones that have been abolished, reinstated, renamed, or moved since you last deployed

Error codes

ERR_TZ_AMBIGUOUS         // 2:30am occurred twice. both are valid. neither is correct.
ERR_DST_SKIPPED_HOUR     // this moment does not exist. your meeting is in it.
ERR_SAMOA_CROSSED_DATELINE // Samoa deleted Friday 30 Dec 2011. it is gone.
ERR_KIRIBATI_AHEAD       // UTC+14 should not be possible. it is.
ERR_RAILS_TIMEZONE_MISMATCH // your app thinks it's UTC. your DB disagrees. good luck.
ERR_INTERVIEW_SCHEDULED_PST // interviewer was in PDT. candidate missed it. hired anyway.
WARN_LORD_HOWE_ISLAND    // UTC+10:30 in winter, UTC+11 in summer. 30 minute DST. intentional.

Known bugs

Arizona does not observe daylight saving time except for the Navajo Nation, which does, except for the Hopi Reservation inside it, which does not. This is not a joke.
Every programming language reinvents timezone handling incorrectly before discovering the IANA database at 2am.
The concept of "now" becomes meaningfully undefined at scale. See also: simultaneity, loneliness.
Scheduling a recurring meeting across DST boundaries produces a new event each time called "did this used to be an hour earlier."

Changelog

v1884.0.0   initial commit. washington dc conference. only 25 of 41 countries signed.
v1918.0.1   US adopts DST for WWI. repeals it immediately after. classic.
v1967.3.0   Uniform Time Act. attempt at standardization. arizona opts out.
v2007.11.0  US extends DST by 4 weeks. all timezone tables globally need patching.
v2011.12.29 Samoa moves across dateline. thursday skipped. not recoverable.
v????       — [RECORD CORRUPTED] —

Edge cases

You are scheduling across Nepal (UTC+5:45). Your calendar app silently rounds. The meeting is now 15 minutes in the past before it begins.
"Tomorrow" in a chat message sent at 11:58pm PST from someone in Tokyo refers to four different calendar dates depending on who is reading it.
the present moment does not have a canonical timezone. this should bother you more than it does.

drafting spec…