Timezone World Map

Why "what time is it there?" is harder than it looks

The Earth turns 360 degrees in 24 hours, so every 15 degrees of longitude corresponds to roughly one hour of solar time. To keep clocks practical, the world is divided into time zones, each defined as an offset from Coordinated Universal Time (UTC) — the modern successor to GMT. New York is normally UTC−5, Tokyo is UTC+9, and the difference between them is the simple subtraction 9 − (−5) = 14 hours. This map shades 25 vertical bands, one per whole-hour offset from UTC−12 to UTC+12, so you can see at a glance how far ahead or behind any region runs.

Click any colored band and the tool computes that band's current time directly from your device's clock: it takes the present moment, converts it to UTC by removing your local offset, then adds the band's offset. That single calculation is what turns a static map into a live one.

A worked example: scheduling across three cities

Say it is 09:00 in London (UTC±0) and you want to call colleagues in New York and Singapore. New York sits at UTC−5, so subtract five hours: it is 04:00 there — far too early. Singapore is UTC+8, so add eight hours: 17:00, the end of their workday. The only window where London morning, New York morning, and Singapore evening overlap is narrow, which is exactly the kind of conflict the city sidebar makes obvious. Each of the 12 cities updates every second, so you never have to do this arithmetic in your head — you read three live clocks side by side.

The part people get wrong: offsets are not fixed

The colored bands assume a clean whole-hour offset, but real timezones drift twice a year. The city clocks in the sidebar are smarter than the bands: they are computed with the browser's built-in Intl timezone engine using IANA zone names like America/New_York and Asia/Kolkata. That engine knows the actual rules for each region, including:

• Daylight Saving Time. London is UTC±0 in winter but UTC+1 in summer; New York swings between UTC−5 and UTC−4. The map band shows the standard offset, but the city clock shows the currently correct one.
• Half-hour and 45-minute zones. India runs at UTC+5:30 and Mumbai's clock reflects that exactly — something a whole-hour band can only approximate. Nepal famously uses UTC+5:45.
• Southern-hemisphere reversal. When the northern hemisphere "springs forward", Sydney is doing the opposite, so the gap between London and Sydney is not constant year-round.

This is why the sidebar shows São Paulo, Sydney, and Toronto with their live offsets rather than trusting a fixed number. If a city clock and the band you clicked disagree by an hour, daylight saving is usually the reason — and the city clock is the one to trust.

Practical uses

• Booking meetings with remote teammates without an off-by-one-hour mistake.
• Catching live events — a product launch announced for "10 AM PT" or a match kicking off in another country.
• Calling family abroad at a polite hour instead of waking them at 3 AM.
• Coordinating deployments or trades tied to a specific market's opening bell.

Tips that prevent timezone bugs

• Anchor to UTC, then convert. Reasoning "London is X, so the other city is X ± offset" is more reliable than counting hours on a map.
• Always confirm around DST changeovers. The two or three weeks where one country has switched and another hasn't are when scheduling errors spike.
• Name the zone, not the offset. "9 AM Eastern" is unambiguous; "9 AM UTC−5" silently breaks when New York moves to UTC−4 in summer.
• Check the date, not just the clock. When it is late evening in New York it is already the next calendar day in Singapore — the sidebar shows each city's date for exactly this reason.

Where the time comes from

Everything runs locally in your browser. The clocks read your computer's system time and apply timezone rules with the standard Intl.DateTimeFormat API — no server is queried, so the map works offline and nothing about your location leaves the page. The trade-off is that accuracy depends on your own device clock being set correctly; if your computer's time is wrong, every city here will be wrong by the same amount.