What the World Time Zones page shows
This page is a world clock. The top panel shows your own local time, date and the time-zone name your browser reports (for example Europe/Berlin). Below it, a 24-hour strip runs from UTC−12 to UTC+14 and marks which whole-hour offsets are currently in daytime or at night. The city grid shows the current time, date and UTC offset for 25 major cities, and you can search or add 25 more, such as Kathmandu, Tehran, Lagos and Vancouver, to a personal watchlist. It is handy for scheduling calls across continents, checking whether a colleague is still at work, or planning travel.
How to use it
- Read your local time at the top; it ticks every second.
- Scan the 24-Hour Timezone Strip. Each slot shows a UTC offset and its current hour, with a sun for 06:00–19:59 and a moon otherwise. Your own offset is highlighted.
- Type in Search city to filter the cards. Searching looks through all 50 built-in cities, not only the ones shown by default.
- Press + Add City and pick a city to add it to Your Watchlist. Remove it again with the × on its card.
How the times are calculated
No time server is contacted. The page reads your device's clock and converts it with the browser's built-in Intl.DateTimeFormat API, passing each city's IANA time-zone name (such as America/New_York or Asia/Kolkata). The browser's own time-zone database supplies the offsets and daylight-saving rules, so a city switches between standard and summer time automatically on the right date. Clocks refresh every second and the strip every minute. Cards shaded dark are cities where it is currently between 20:00 and 05:59.
Your watchlist is saved in your browser's localStorage under the key tz_watchlist, so it survives reloads on the same device and browser. It is never sent to a server, and clearing your site data removes it.
Accuracy and limitations
- If your computer's clock is wrong, every time on the page is wrong by the same amount. Most devices keep their clock in sync automatically.
- Daylight-saving and offset changes are only as current as your browser's time-zone data; an outdated browser may miss a rule change that a government announced recently.
- The strip only shows whole-hour offsets, so zones like India (UTC+5:30), Tehran (UTC+3:30) and Nepal (UTC+5:45) are not drawn as separate slots, and the highlighted local slot is rounded to the nearest hour. The city cards always show the exact offset.
- On older browsers that do not support short offset names, the UTC offset line on a card may be blank.
- Beijing and Shanghai both use the Asia/Shanghai zone, so they always show the same time.
Frequently asked questions
Does it handle daylight saving time?
Yes. Because each city is identified by its IANA zone, the browser applies that region's daylight-saving rules for today's date. Cities in places without summer time, such as Tokyo or Singapore, keep the same offset all year.
What is UTC?
Coordinated Universal Time is the reference time scale that all offsets are measured from. It replaced Greenwich Mean Time as the civil standard and does not change with the seasons.
Why are there more than 24 time zones?
Some regions use half-hour or 45-minute offsets, and a few Pacific islands sit at UTC+13 or UTC+14 so that they share a calendar day with their trading partners. That is why the strip runs beyond UTC+12.
Is my location used?
No. The page never asks for your location; it only reads the time zone your browser and operating system are already set to.