World Clock

What the World Clock Does

It displays a row of clocks, one per city, each showing the local time there right now. It is the quick way to check whether it is a reasonable hour to call a colleague in another country, or to coordinate a meeting across time zones.

The cities are a fixed set of major hubs across the Americas, Europe, the Middle East, Asia and Australia. Each clock updates on its own so the whole board stays current as you watch.

How It Works

The tool takes the current moment from your device and re-expresses it in each city's time zone using the browser's built-in internationalisation and time-zone database. That database knows each zone's offset from universal time and its daylight-saving rules, so the displayed times shift correctly when clocks change.

It refreshes every few seconds, formatting each city's time as hours and minutes on a 24-hour clock. Because it reads from your device, every clock is anchored to the same underlying moment — they differ only by their time-zone offsets.

Generation algorithm

1. Read the current moment. Take the current time from your device.
2. Apply each time zone. Convert that moment into each city's local time using the browser's time-zone database.
3. Format the clocks. Show each city's time as hours and minutes on a 24-hour clock.
4. Refresh. Update every few seconds so the times stay current.

Cities shown

A fixed set of major hubs; each is shown in 24-hour local time with daylight saving applied automatically.

Technical Details

Standards & references

• IANA time-zone database — the browser identifies each city by an IANA zone name (such as America/New_York) and applies that zone's offset and daylight-saving rules — the same database most systems use.
• Automatic daylight saving — because the time-zone data carries each region's clock-change rules, the displayed times adjust on their own when daylight saving starts or ends.
• Depends on the device clock — every clock is anchored to your device's current time, so if your device clock is wrong, all the cities are off by the same amount.

Accuracy & Limitations

The clocks are only as accurate as your device. Every city is calculated from your device's current time, so a device clock that is a few minutes off makes all of the cities a few minutes off too. Keep your system clock set to update automatically.

Daylight saving is handled by the browser's time-zone data, which is kept up to date with the rules in each region. On the rare occasion a country changes its rules at short notice, the displayed time follows whatever your browser's data currently says.

It shows a fixed set of nine cities and cannot be customised here. If your city is not listed, pick the nearest one in the same time zone — the offset is what matters, not the city name.

It shows hours and minutes on a 24-hour clock, with no seconds and no date. For the exact second or the calendar date in a zone, use a tool that shows them.

It refreshes every few seconds rather than every second, so a clock can be a little behind the true minute change. Wait a moment for it to catch up.

Real-World Use Cases

When to use it — and when not to

Need a specific city not listed, or a future time across zones? Use a full time-zone converter. Converting a Unix timestamp to a date? Use a timestamp converter.

Frequently Asked Questions

References

• Intl.DateTimeFormat (MDN Web Docs)
• tz database (Wikipedia)
• Daylight saving time (Wikipedia)

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