How does this tool know the correct time without an internet connection?

It uses the IANA time-zone database that is already built into every modern browser and operating system. The Intl.DateTimeFormat API reads your device clock (which is already synchronised via NTP) and applies the correct UTC offset and daylight-saving rule for the chosen location. No network request is made.

Does it handle daylight saving time automatically?

Yes. The browser's Intl engine applies the DST rule for every zone at the exact moment you look up the time. If a city is currently observing summer time, you will see the summer offset — for example London shows UTC+1 in summer and UTC+0 in winter, Tokyo always shows UTC+9 because Japan does not observe DST.

What about half-hour and quarter-hour offsets?

These are fully supported. India (UTC+5:30), Iran (UTC+3:30), Afghanistan (UTC+4:30), Nepal (UTC+5:45), and the Chatham Islands (UTC+12:45 in winter / UTC+13:45 in summer) all display the correct fractional offset because the calculation reads the raw zone offset from Intl rather than rounding to the nearest hour.

Why does the daytime indicator say night even though it seems bright outside?

The day/night boundary used here is a simple threshold — 06:00 to 20:00 local time is classed as daytime. It does not account for latitude or season. At high latitudes (Reykjavik in summer, for instance) it may still be light well past 20:00. For precise sunrise and sunset times, use a dedicated astronomical calculator.

My city is not in the list — what should I do?

Search by country name or a nearby major city that shares the same time zone. For example, most of England and Wales share Europe/London; most of eastern Australia shares Australia/Sydney or Australia/Melbourne. All cities within the same IANA zone always show identical times.

Is the time accurate to the second?

The clock updates every second using your device's system time. Most devices synchronise with an NTP server automatically and stay within a fraction of a second of true UTC. The displayed seconds are therefore accurate to within roughly one second of real world time.

What Time Is It In…?

Ever needed to know the time in another part of the world right now — before sending a message, booking a call, or just satisfying curiosity? This tool gives you a live, ticking local clock for any city or country on Earth, calculated entirely inside your browser using the same time-zone engine your operating system relies on.

Type a city name — Tokyo, Nairobi, Buenos Aires, Tehran — or a country name, select from the dropdown, and a large clock face appears showing the current local time, today’s date and day of the week, the UTC offset (including any fractional-hour offset), and a simple indicator of whether it is daytime or night-time there. Your own current time and the exact difference from the target city are shown side by side so you can judge at a glance whether it is a reasonable hour to call.

How it works

The tool uses the browser’s built-in Intl.DateTimeFormat API with IANA time-zone names — the same standard database that underpins macOS, Windows, Linux, Android, and iOS. When you select a city, the code calls:

Intl.DateTimeFormat("en-GB", { timeZone: "Asia/Tokyo", ... }).format(now)

where now is the current instant from Date.now(). The browser looks up the IANA zone entry for that identifier, finds the UTC offset that applies at this exact moment (accounting for DST transitions), and formats the local wall-clock time. Because the offset calculation is done by the platform — not by a hard-coded lookup table — it automatically stays correct across daylight-saving transitions, historical zone changes, and the unusual half-hour or quarter-hour offsets used by India, Iran, Nepal, Afghanistan, and the Chatham Islands.

The clock ticks via a one-second setInterval that updates the displayed time reactively. Nothing is fetched from a remote server at any point.

Worked example

Suppose you are in London (UTC+1 in British Summer Time) and it is 14:30 on a Tuesday afternoon. You want to know whether your colleague in Tokyo is still in the office.

Tokyo uses the Asia/Tokyo zone, which is fixed at UTC+9 year-round (Japan does not observe DST). The offset difference is 9 − 1 = 8 hours ahead, so it is currently 22:30 on Tuesday in Tokyo. The daytime indicator will show the moon icon, and the difference label will read “8h ahead of you” — a clear signal that your colleague has likely finished for the day.

Your city	Your time	Target city	Their time	Difference
London (BST)	14:30 Tue	Tokyo	22:30 Tue	+8 h
London (BST)	14:30 Tue	New York (EDT)	09:30 Tue	-5 h
London (BST)	14:30 Tue	Mumbai	19:00 Tue	+4 h 30 m
London (BST)	14:30 Tue	Los Angeles (PDT)	06:30 Tue	-8 h

Notice that Mumbai shows a 30-minute difference from a whole-hour boundary. This is not an error — India’s standard time is UTC+5:30 by design, and the tool reports it correctly.

UTC offset formula note

The UTC offset is derived by comparing the wall-clock time in the requested zone against the UTC instant:

offset_minutes = (zone_wall_clock_as_UTC - true_UTC) / 60000

This is computed in real time from Intl.DateTimeFormat.formatToParts() rather than from a static lookup, so it is always exact for the current moment regardless of DST state. The displayed offset uses the conventional sign: positive means east of UTC (ahead), negative means west of UTC (behind). For fractional offsets the result is shown as, for example, UTC+5:30 or UTC+5:45 rather than a decimal.