World Clock

What Is a World Clock?

A world clock displays the current local time in multiple cities or time zones simultaneously — so you can see at a glance what time it is in New York while you're sitting in London, or know whether your contact in Tokyo is likely awake or asleep before you press send. Before the internet, world clocks were physical devices found in newsrooms, airport terminals, and trading floors. Today, a free world clock in your browser does the same job instantly, without the wall of physical clocks.

The core function is simple: each city runs on its own local time, determined by its position in a time zone. The world is divided into 24 primary time zones, each one hour apart, measured as an offset from Coordinated Universal Time (UTC). New York is UTC−5 in winter and UTC−4 during daylight saving time. Tokyo is UTC+9 year-round. The world clock above accounts for all of this automatically — including daylight saving changes — so you always see the correct current local time.

Understanding UTC and Time Zone Offsets

UTC — Coordinated Universal Time — is the global standard against which all local times are measured. It replaced Greenwich Mean Time (GMT) as the international reference in 1967, though the two are functionally identical for everyday purposes. When you see "UTC+9," it means that location's clocks run 9 hours ahead of UTC. "UTC−5" means 5 hours behind.

Not all time zones fall on clean whole-hour boundaries. India runs at UTC+5:30, Nepal at UTC+5:45, and parts of Australia use UTC+9:30. Iran is UTC+3:30. These half-hour and quarter-hour offsets exist for historical and geographic reasons — they reflect decisions made by individual countries to align their clocks with their solar noon while staying close to neighboring zones.

Daylight Saving Time (DST) adds another layer. Countries in North America and Europe shift their clocks forward one hour in spring and back in autumn, effectively changing their UTC offset twice a year. Japan, China, India, and most of the equatorial world do not observe DST, which means the offset between two cities can shift by an hour depending on the time of year. The world clock on this page uses your browser's timezone database, which is always kept current.

Practical Uses for a World Clock

The most common use case is scheduling calls or meetings across time zones. If you're in Los Angeles (UTC−8 in winter) arranging a call with someone in London (UTC+0), you need to know that 9 AM your time is 5 PM for them — workable, but barely. Add a colleague in Singapore (UTC+8) and the overlap shrinks to almost nothing. A world clock lets you see all three at once and find a time that works.

World clocks are also useful for following financial markets. The New York Stock Exchange opens at 9:30 AM Eastern. The London Stock Exchange opens at 8 AM GMT. The Tokyo Stock Exchange opens at 9 AM JST. For investors and traders keeping an eye on global markets, knowing the local time in each financial center is practical, not optional.

Travelers find world clocks valuable when planning itineraries, booking international flights (departure and arrival times are often shown in local time at each city), or simply keeping in sync with family back home during a trip. And for anyone managing remote teams across continents, a world clock is the single most useful tool for basic coordination — more practical than any scheduling app, and always free.

Frequently Asked Questions