Time Zone Converter & World Clock

Who it is for

It is for arranging a call, a class or a hand-over between two of the listed places, and for checking whether it is a reasonable hour there right now. It compares one moment in two cities; it does not build a schedule or show overlapping working hours.

How a local time is resolved

Each city is stored with an IANA time-zone identifier such as Europe/London or America/Sao_Paulo. To turn the clock time you typed into a real moment, the page tries candidate instants and asks the browser's Intl.DateTimeFormat what the wall-clock reading in that zone would be, keeping the candidate whose reading matches what you entered.

Because the answer comes from the browser's copy of the time-zone database, the daylight-saving rule in force on the date you chose is applied automatically — including rules that differ from today's. Nothing about summer time is hard-coded in the page.

Two clock readings cannot be resolved that way, and both are reported instead of guessed:

• A time the clocks skipped. Entering 02:30 on 8 March 2026 in New York returns "This local time does not exist during a daylight-saving change. Choose another time."
• A time the clocks repeated. Entering 01:30 on 1 November 2026 in New York returns "This time occurs twice during a daylight-saving change. Choose a time outside the repeated hour."

Results are shown to the minute on a 12-hour clock, with the destination's calendar date on the second line, so a conversion that crosses midnight is unambiguous.

Two verified examples

The United Kingdom returns to GMT on the last Sunday of October, while the United States leaves daylight time on the first Sunday of November. In 2026 that leaves a nine-day window in which New York and London are four hours apart rather than the usual five:

1. 09:00 on Wednesday 28 October 2026 in New York converts to 01:00 PM in London — a four-hour gap, because New York is still on daylight time and London is already back on GMT.
2. 09:00 on Wednesday 4 November 2026 in New York converts to 02:00 PM in London — the five-hour gap most people expect. The only thing that changed is the date.

A third case shows the date line on the result: 22:00 on Thursday 15 January 2026 in London converts to 09:00 AM in Sydney, and the detail line reads "On Fri, Jan 16, 2026 in Sydney".

Supported cities

Twenty cities are built into the page. Several stand in for a whole zone: Islamabad uses Asia/Karachi, Mumbai uses Asia/Kolkata, Beijing uses Asia/Shanghai and Rio de Janeiro uses America/Sao_Paulo.

Favourite cities

The star on a clock card adds that city to a short list that appears above the full grid. The list is the city names only, saved in your browser's local storage under the key favoriteCities, and it is read back each time the clocks are drawn.

That means favourites survive a reload but belong to one browser on one device: they do not follow you to a phone, another browser or a private window, and clearing site data removes them. Nothing is sent to a server, so there is no account to sign in to.

Common mistakes

• Using today's difference for a future date. Enter the actual date of the meeting. Between late March and early November the gap between Europe and North America changes twice, and the southern hemisphere moves the other way.
• Quoting the fixed label. Saying "3 PM GMT" in July is wrong for London; it is British Summer Time then. Quote the city and the local clock time instead of an abbreviation.
• Assuming whole-hour offsets. Mumbai is thirty minutes off the hour, so 17:00 in London is 22:30 there in January and 21:30 in July.
• Trusting the world clock on a device with a wrong clock. Those cards are your device's current moment formatted for each zone. If the device clock is off, every card is off by the same amount.
• Misreading midnight. On a 12-hour display 00:30 appears as 12:30 AM. Check the date on the second line.

Limits

• Only the twenty cities above. There is no search across the full time-zone database and no way to add a city.
• One moment at a time. No recurring events, no calendar invitations, no shareable link.
• Hours and minutes only; no seconds, and no UTC offset shown alongside the result.
• Time-zone rules come from the browser and operating system. Governments change them at short notice, so a device that has not been updated can be wrong about a future date.
• For a flight, an examination or a contractual deadline, confirm the time against the organisation's own notice.

Questions