tzdiff

Compare timezones at a glance. For humans, not crontabs.

$ tzdiff IDT PST UTC TYO
idt      tue 14:30  apr 28  +0300
pst      tue 04:30  apr 28  -0700
utc      tue 11:30  apr 28  +0000
tyo      tue 20:30  apr 28  +0900

Why tzdiff

Scheduling a sync between Tel Aviv, San Francisco, and Tokyo in your head is a tax. The website-based timezone converters take two clicks per zone and break in incognito because they want your localStorage. Your terminal already knows the right answer; it just doesn't print it in a comparable shape. dig for DNS, tzdiff for time.

Install

npm install -g @v0idd0/tzdiff

Usage

# Current time in multiple zones
tzdiff IDT PST UTC TYO

# Use IANA names too
tzdiff Asia/Tokyo Europe/London America/New_York

# Specific moment in time
tzdiff --at "2026-04-28 09:00 UTC" PST EST IST

# JSON for scripting
tzdiff --json UTC IDT TYO | jq '.[] | .time'

Supported aliases

Americas: PST, PDT, MST, MDT, CST, CDT, EST, EDT, AKST, HST Europe: GMT, UTC, BST, CET, CEST, EET, EEST, MSK Middle East: IDT, GST, AST Asia: IST (India), PKT, ICT, WIB, HKT, SGT, JST, TYO, KST Oceania: AEDT, AEST, SYD, ACDT, AWST, NZDT, NZST

Anything else → use the IANA name directly (America/Sao_Paulo, Africa/Cairo, etc.).

Compared to alternatives

| tool | offline? | DST aware | output for grep/Slack | install | |---|---|---|---|---| | tzdiff | yes | yes (via Intl/IANA) | yes, aligned columns | one npm install | | date -u chains | yes | partially | requires shell-fu | bundled with OS | | World Time Buddy / time.is | no | yes | screenshot only | web | | tz (older CLI) | yes | yes | column drift | unmaintained |

Tools like timeanddate.com handle the broader case (recurring meetings, DST historical lookups). tzdiff is the speed-of-typing case: you have 4 abbreviations in your head and want a 4-row answer in 200ms.

FAQ

Why "IST" defaults to India and not Israel? Because India is +0530 year-round and Israel toggles between IST/IDT seasonally. We default IST to India to avoid quietly changing meaning twice a year. For Israel use IDT (summer) or Asia/Jerusalem.

Does --at accept your home timezone? Pass it explicitly: --at "2026-07-31 17:00 PDT". The parser accepts <datetime> <tz> in that order.

Will it ever DST-jump output rows? Each row is computed independently against its zone's TZ database, so yes — running on the spring-forward Sunday will show the forward jump in the affected zone only.

Can I save a recurring meeting? No. tzdiff is one-shot by design. For recurring time-math, use a calendar app — that's a different problem.

Programmatic API

import { compare, format } from '@v0idd0/tzdiff';

const rows = compare(['UTC', 'IDT', 'TYO']);
console.log(format(rows));

// Or with a specific moment:
const at = new Date('2026-07-31T17:00:00Z');
const rows = compare(['PST', 'IDT'], at);

Tips for meeting math

• Pin one zone as your anchor. When scheduling, write the time once in UTC and let recipients run tzdiff --at "2026-05-12 14:00 UTC" <their zone> — eliminates the "is that 2pm yours or mine" thread.
• DST-sensitive ranges. If a meeting falls within a few weeks of a DST boundary, run tzdiff for both pre- and post-boundary dates; the zones won't always agree on which week the change lands.
• Slack format. The aligned columnar output pastes cleanly into Slack code blocks (\```) — no Markdown table conversion needed.

More from the studio

This is one tool out of many — see from-the-studio.md for the full lineup of vøiddo products (other CLI tools, browser extensions, the studio's flagship products and games).

License

MIT.

Built by vøiddo — a small studio shipping AI-flavoured products, free dev tools, Chrome extensions and weird browser games.