World Clock

Times come from your browser's IANA time zone data. The offset badge on each card shows the city's current UTC offset — updated automatically when a region enters or leaves daylight saving — so you can also compute the time from UTC by hand.

How time zones actually work

The world's clocks are all defined relative to one reference: Coordinated Universal Time, or UTC, kept by an international network of atomic clocks. A time zone is simply an offset from that reference. Tokyo runs nine hours ahead of UTC all year; New York runs five hours behind in winter and four in summer. When you know a city's offset, converting is arithmetic — but the offsets themselves are political decisions, not geographic ones, which is why the map of time zones follows borders rather than clean lines of longitude.

Two details trip people up. First, offsets are not all whole hours: India uses UTC+5:30, Nepal UTC+5:45, and parts of Australia UTC+9:30. Second, "the time in a country" is often ambiguous — the United States spans six zones, Russia eleven, while China officially uses a single zone (UTC+8) for its entire width, meaning the sun can rise after 9 a.m. in its far west.

Why daylight saving time complicates everything

Roughly 70 countries shift their clocks seasonally, and they don't do it on the same dates. The United States springs forward on the second Sunday of March, but the European Union waits until the last Sunday of the month. For those two or three weeks, the usual 5-hour gap between New York and London shrinks to 4 — an annual ambush for anyone scheduling transatlantic calls. The southern hemisphere flips the whole pattern: when Sydney is on daylight time (October to April), London is not, and vice versa, so the gap between them swings between 9 and 11 hours across the year.

This is why a serious world clock can't just store one offset per city. This page asks your browser for the current rules from the IANA time zone database, the reference dataset that tracks every zone's DST schedule and its historical changes going back decades. For the full picture, see the guide to daylight saving time.

Reading the grid

Cities are ordered from the earliest local time (Auckland, which greets each date first among major cities) to the latest (Los Angeles). A quick rule of thumb for meetings: the "golden window" for a call spanning the US East Coast, Europe, and India is roughly 8–10 a.m. in New York — early afternoon in London, evening in Mumbai. There is no hour of the day when New York, London, and Sydney are all inside normal business hours; someone always takes the early morning or the late night.