How this world clock works
The times come from your device's clock plus the IANA time zone database that's built into your browser. Airlines, banks and operating systems use the same database, and it updates whenever a government changes its rules, so daylight saving is always right without this site doing anything. An amber bar means it's daytime in that city (6:00 to 20:00). A dark bar means night. Your city list is saved on your own device and nowhere else.
Reading the clocks like a pro
Each card tells you more than the time. The date line says whether that city is on the same day as you, already on tomorrow, or still on yesterday. The UTC offset, like UTC+9 for Tokyo, is how far the city sits from Coordinated Universal Time, the reference clock the whole world measures against. To get the gap between two cities, subtract the offsets. Tokyo is UTC+9 and New York is UTC−4 in summer, so Tokyo runs 13 hours ahead.
Why some cities surprise you
Not every zone is a whole hour. India runs on UTC+5:30, Nepal on UTC+5:45, and parts of Australia use half hours too, so Mumbai can be nine and a half hours ahead of New York. Big countries slice themselves up differently. The mainland United States has four zones. China has one, and all of it runs on Beijing time. Russia has eleven. And because daylight saving is a political choice, the gap between two cities can change during the year. London and New York are usually five hours apart, but for a couple of weeks in late March they're four, because the US has switched to summer time and the UK hasn't yet.
Frequently asked questions
How accurate are these clocks?
Exactly as accurate as your device's clock, which on phones and modern computers is synced automatically to network time and typically within a second of official time. The site adds no delay of its own — clocks tick locally in your browser.
Does it handle daylight saving time?
Yes, automatically, for every city — including places that don't observe DST at all (most of Asia and Africa) and southern-hemisphere countries whose summer time runs opposite to Europe and North America.
Can I use this offline?
Once the page has loaded, the clocks keep running without a connection — the time zone math happens entirely on your device.
Need to schedule across these zones? The converter translates a specific date and time between cities, and the meeting planner finds hours that work for everyone. Curious how zones came to be? Read time zones explained.