timezone.fyi

Source for timezone.fyi — a tool for sharing a time across multiple time zones

How it works

URLs encode a time and one or more zones:

https://timezone.fyi/10:30am,pst,est
https://timezone.fyi/2pm,JFK,LHR,NRT
https://timezone.fyi/my-meeting/10am,NYC,LON,TOK

• First segment — time string (10am, 10:30am, 10am-2pm for a range)
• Remaining segments — timezone codes, separated by commas or periods
• Optional label — prefix the time with label/ to name the event

Accepted zone formats:

• Timezone abbreviations: PST, EST, GMT, IST
• City aliases: NYC, LON, TOK, SF
• GMT offsets: GMT+5, GMT-8
• IANA names: America/New_York, Europe/London
• Airport codes: JFK, LHR, NRT, DXB (~9,800 airports)
• Metro area codes: NYC, LON, TYO, PAR, CHI (full list)

The page also generates a .ics calendar file download for the time.

Architecture

static/          → landing page, CSS, client JS (served as static assets)
netlify/
  functions/
    index.js     → main request handler (Netlify Function v2)
    og.js        → Open Graph image generation
  common.js      → timezone parsing and calculation logic
  airport-map-data.json  → precomputed IATA → IANA timezone map (~9,800 airports + metro codes)
scripts/
  build-airport-map.mjs  → regenerates airport-map-data.json from source data

All routing is handled server-side by the Netlify function — the URL path is parsed directly, no client-side routing.

Dev setup

Requirements: Node 20+, Netlify CLI

npm install        # must be run with Node 20+ — canvas has a native binary tied to the Node version
npm run dev        # starts local dev server at http://localhost:8888
npm test           # runs the full test suite

Note: Use npm run dev, not netlify dev directly. The netlify.toml has a [dev] section that must be read from this directory — running the CLI directly can cause it to traverse up to a parent git repo and load the wrong files.

Node version: canvas uses a prebuilt native binary tied to the Node version it was installed under. If you switch Node versions and see a NODE_MODULE_VERSION mismatch error from /og, re-run npm install to fetch the matching binary for your current Node version (20+).

Regenerating the airport map

netlify/airport-map-data.json is a precomputed map of IATA codes → IANA timezone strings, covering ~9,800 airports plus metropolitan area codes. It's committed so no download is needed at runtime or install time.

Data is sourced from lxndrblz/Airports and fetched at build time — no local files required:

npm run build:airports

The build script fetches airports.csv and citycodes.csv directly from GitHub.

Deployment

Deployed on Netlify. Push to main to deploy.