World Clock

The world clock displays the current local time in major cities around the world simultaneously, updating in real time. It is designed for remote teams, international travellers, business professionals, and anyone who regularly communicates across time zones.

How to Use the World Clock

1. The world clock displays a default selection of major cities when you open it.
2. Add any city by typing its name into the search field and selecting it from the results.
3. Remove cities you do not need by clicking the remove icon next to them.
4. Pin frequently used cities to keep them at the top of your list.
5. The times update automatically every second; no refresh is needed.

The Formula

Every time zone on Earth is defined by its UTC offset: the number of hours (and sometimes minutes) ahead of or behind Coordinated Universal Time (UTC). The world clock fetches your device's system clock and converts it to each displayed time zone.

Local time in zone Z = UTC time + UTC offset for zone Z

The UTC offset accounts for both the standard time offset for the region and any active Daylight Saving Time (DST) adjustment. For example:

• London in winter: UTC+0 (GMT). Time = UTC + 0.
• London in summer: UTC+1 (BST). Time = UTC + 1.
• New York in summer: UTC-4 (EDT). Time = UTC - 4.
• Tokyo: UTC+9 (JST). Time = UTC + 9 (Japan does not observe DST).

Real-World Example

Your team has members in London, New York, and Singapore. Today is a summer weekday (June).

• London (BST): UTC+1. If UTC is 14:00, London time is 15:00.
• New York (EDT): UTC-4. UTC 14:00 = 10:00 AM New York time.
• Singapore (SGT): UTC+8. UTC 14:00 = 22:00 Singapore time.

The window for a call that suits all three locations is narrow. Morning New York time (10:00-12:00 EDT) maps to London afternoon (15:00-17:00 BST) and Singapore late evening (22:00-00:00 SGT). This demonstrates why a world clock and meeting planner are essential tools for global teams.

Understanding UTC Offsets and DST

UTC (Coordinated Universal Time) is maintained by atomic clocks and does not change with the seasons. Every time zone is a fixed offset from UTC for standard time. When Daylight Saving Time is active, the offset increases by one hour. Not all countries observe DST:

• Countries that do NOT observe DST include Japan, China, India, most of Africa, and most of South/Southeast Asia.
• Countries that DO observe DST include most of Europe, North America, and Australia.
• DST transition dates vary by country. The US and EU shift on different weeks, creating a period where the offset between them changes temporarily.

Fractional offsets exist because some time zones are based on historical solar time rather than political boundaries. India (UTC+5:30), Iran (UTC+3:30), and Nepal (UTC+5:45) are notable examples.

Frequently Asked Questions

What is the difference between GMT and UTC? GMT (Greenwich Mean Time) and UTC refer to the same clock time, but they are different concepts. GMT is a time zone; UTC is a time standard maintained by atomic clocks. In practice, they are interchangeable for everyday purposes. The UK observes GMT in winter and BST (UTC+1) in summer.

Why do some countries span multiple time zones? Large countries cover enough geographic longitude that the solar time differs significantly between their eastern and western edges. Russia has 11 time zones. The United States has 6 (including Alaska and Hawaii). China, despite its geographic size, uses a single time zone (UTC+8) for political unity, meaning sunrise and sunset times vary enormously across the country.

How accurate is the world clock? The world clock reads your device's system clock, which syncs to internet time servers (NTP) and is accurate to within milliseconds. The displayed city times are accurate as long as the UTC offset data is up to date, particularly around DST transitions.

How do I find the best time for an international meeting? Look for the overlap between normal working hours (roughly 9:00-18:00) across all relevant time zones. The meeting planner tool automates this by highlighting the shared working window for selected cities.

One instant read in nine cities

Pick one absolute instant and read it across the city list. The table below uses 14:00 UTC on Monday 15 June 2026, which sits inside British Summer Time and inside North American daylight time.

Two rows cross a date boundary. Tokyo is an hour short of midnight while Sydney has already moved into Tuesday. The London to New York gap reads as five hours in the table, and the London to Sydney gap as nine.

The same instant in January, for contrast

Running the same instant in winter shows which offsets move with the season and which hold.

Four of the nine cities hold the same offset all year, and Sydney moves in the opposite direction to Europe. London and New York keep a five hour gap across both months because their clocks change a week apart at most in this pair of months, while the London to Sydney gap widens from nine hours to eleven.

How a displayed time is built

Local time in a zone equals UTC time plus the offset for that zone. The offsets come from the zone database that browsers carry, which holds each region's rules rather than a single fixed number, so a city's offset changes on the dates its government sets.

The 2026 transition dates are worth writing down. In the United Kingdom the clocks go forward on Sunday 29 March and back on Sunday 25 October, which the GOV.UK clock change page lists. Most of Europe follows the same two Sundays. In the United States the change falls on the second Sunday in March and the first Sunday in November, which in 2026 are 8 March and 1 November. Australia runs the other way around the year, ending summer time on the first Sunday in April, which is 5 April 2026, and starting it again on the first Sunday in October, which is 4 October 2026.

Four of the cities in the list above sit at a fixed offset, and the rest move by an hour. Fractional offsets exist where a zone sits on a half or quarter hour rather than a whole one. Mumbai is the case on this list at plus 5 hours 30 minutes, and the offsets section above names Iran at plus 3 hours 30 minutes and Nepal at plus 5 hours 45 minutes.

Checking a converted time by hand

A conversion can be checked without the tool. Add the offset to the UTC hour and read the result: 14 plus 5 gives 19, so the Mumbai row reads 19:30 with the half hour carried over, and 14 plus 9 gives 23, which is the Tokyo row. Where the addition passes 24 the local clock has moved into the next day, which is what happens to Sydney in the June table at 14 plus 10.

The check also catches an offset read with the wrong sign. A city west of Greenwich subtracts from UTC, so New York at UTC-4 reads 10:00 when UTC is 14:00 rather than 18:00. The sign follows the direction of travel rather than the size of the offset, and the June and January tables above give the same city both ways for a reader who wants to test it.

What the page's clock reads and what it adds

The description at the top of this page sets out a live display of major cities, a search field, a control to remove a city, pinning, and a refresh every second. The component behind the page holds a fixed list of nine cities and works them out only when the Calculate button is pressed, so the steps about adding, removing and pinning cities describe something the tool does not do.

One defect sits in the city selector. Every option in the list is written with an empty value, so the selected zone is always the empty string, and asking the browser to format a time for an empty zone raises a range error instead of returning a time. The Mumbai row above is therefore not reachable from the form at all. The fault is in the component and is reported for its owner rather than patched in this batch.

Also try these free tools:

• Time Zone Converter
• Meeting Planner
• Timer