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Time Zone Converter

EST ↔ PST, UTC ↔ Tokyo, with DST handled automatically by the browser.

Time-zone conversion is one of those problems that sounds trivial — “just add three hours” — and stops being trivial the moment daylight saving, half-hour zones, or date boundaries come into play. The converter below uses the browser’s built-in IANA timezone database (the same source curl, Linux, and macOS rely on), so the offsets are always current and the DST transitions land on the right day.

2026-05-14 13:26 in New York18:26 on 2026-05-14 in London

Difference: +5h

How to use

  1. Pick your two zones

    The dropdowns show 28 major zones. The current UTC offset is annotated next to each label so you can sanity-check.

  2. Set the date and time

    Date and 24-hour time on the from-zone clock. The result updates as you change either input.

  3. Read the converted time

    The result shows the same instant rendered on the to-zone clock — including the date, which can shift backwards or forwards depending on direction.

Frequently asked questions

How is daylight saving handled?
Automatically. The browser's Intl.DateTimeFormat resolves each conversion against the most recent IANA tzdata bundled with your operating system. Spring-forward and fall-back transitions land on the correct local date.
Why does my converted time show a different day?
Because the two zones are on opposite sides of the international date line, or the conversion crossed midnight. The displayed date is the wall-clock date in the destination zone — exactly what someone there would see on their phone.
What about half-hour and 45-minute zones (India, Nepal)?
Supported. Asia/Kolkata is UTC+5:30 year-round. The widget displays the offset correctly even though it's not a whole-number.
Does the calculator know my local time?
It defaults the date and time to your machine's current local clock when the page loads. Pick any zone — the calculator doesn't assume you're in the from-zone.
Can I add more zones?
Not from the UI yet. The curated list of 28 covers the most-searched zone pairs; suggest additions via the contact page and we'll add them.

About

Why DST is so messy

Most of the world has stopped using DST (most of Asia, Africa, and South America). The US, EU, and Australia still use it, but on different schedules. The widget's reliance on IANA tzdata means the schedule is correct without anyone having to hardcode rules.

What's an IANA timezone?

A region with a single offset history (when it switches to and from DST, plus any historical adjustments). Time zones aren't strictly geographic — they're political. "America/New_York" captures the offset rules for that specific jurisdiction over time.