Time zones are one of humanity's most practical — and occasionally maddening — inventions. Before the mid-nineteenth century, every town kept its own local solar time. When railways began connecting cities across continents, the chaos of hundreds of local times became operationally unworkable. The solution, standardized time zones, was first adopted by British railways in 1847 and formalized globally at the International Meridian Conference in Washington D.C. in 1884, where Greenwich, England was established as the Prime Meridian and the origin of what we now call Coordinated Universal Time (UTC).
Today, the world is divided into 38 distinct UTC offsets — not the neat 24 you might expect from dividing 360 degrees of longitude by 15. Political boundaries, trade relationships, and national identity have all bent the lines. China, for instance, spans five natural time zones but uses a single national time (UTC+8). India, straddling two zones, uses a half-hour offset (UTC+5:30) as a compromise.
GMT vs. UTC: What's the Difference?
The Astronomical vs. Atomic Distinction
The terms GMT (Greenwich Mean Time) and UTC (Coordinated Universal Time) are often used interchangeably, but they are technically distinct. GMT is an astronomical standard based on the mean solar time at the Royal Observatory in Greenwich, London. UTC is an atomic time standard maintained by a network of atomic clocks worldwide and coordinated by the International Bureau of Weights and Measures (BIPM).
When the Difference Matters
In practice, UTC and GMT differ by less than one second at any given moment. For everyday scheduling purposes, they are equivalent. However, for scientific, legal, and technical applications — satellite navigation, financial transactions, network timestamps — UTC is the authoritative standard. When you see a server log timestamp ending in Z, that Z stands for "Zulu time," the military designation for UTC.
The Complete List of UTC Offsets
The table below lists all 37 standard UTC offsets currently in use, from UTC−12:00 in the uninhabited Baker and Howland Islands to UTC+14:00 in the Line Islands of Kiribati — making Kiribati the first territory to enter each new calendar day.
| UTC Offset | Key Locations | DST Observed |
|---|---|---|
| UTC−12:00 | Baker Island, Howland Island | No |
| UTC−11:00 | Samoa (American Samoa) | No |
| UTC−10:00 | Hawaii (USA), Cook Islands | No |
| UTC−09:30 | Marquesas Islands | No |
| UTC−09:00 | Alaska (USA) | Yes |
| UTC−08:00 | Pacific Time (USA/Canada) | Yes |
| UTC−07:00 | Mountain Time (USA/Canada) | Yes |
| UTC−06:00 | Central Time (USA/Canada), Mexico City | Yes |
| UTC−05:00 | Eastern Time (USA/Canada), Bogotá, Lima | Yes |
| UTC−04:00 | Atlantic Time, Santiago, Caracas | Varies |
| UTC−03:00 | São Paulo, Buenos Aires, Greenland | Varies |
| UTC−02:00 | South Georgia Island | No |
| UTC−01:00 | Azores, Cape Verde | Varies |
| UTC±00:00 | London (GMT), Reykjavik, Accra | Varies |
| UTC+01:00 | Paris, Berlin, Rome, Lagos | Varies |
| UTC+02:00 | Cairo, Johannesburg, Helsinki | Varies |
| UTC+03:00 | Moscow, Nairobi, Riyadh | No |
| UTC+03:30 | Tehran (Iran) | Yes |
| UTC+04:00 | Dubai, Baku, Tbilisi | No |
| UTC+04:30 | Kabul (Afghanistan) | No |
| UTC+05:00 | Karachi, Tashkent, Yekaterinburg | No |
| UTC+05:30 | Mumbai, Delhi, Colombo | No |
| UTC+05:45 | Kathmandu (Nepal) | No |
| UTC+06:00 | Dhaka, Almaty, Omsk | No |
| UTC+06:30 | Yangon (Myanmar) | No |
| UTC+07:00 | Bangkok, Hanoi, Jakarta | No |
| UTC+08:00 | Singapore, Beijing, Perth, Kuala Lumpur | No |
| UTC+08:45 | Eucla (Australia) | No |
| UTC+09:00 | Tokyo, Seoul, Yakutsk | No |
| UTC+09:30 | Adelaide, Darwin (Australia) | Varies |
| UTC+10:00 | Sydney, Melbourne, Brisbane | Varies |
| UTC+10:30 | Lord Howe Island | Varies |
| UTC+11:00 | Honiara, Noumea | No |
| UTC+12:00 | Auckland, Fiji, Kamchatka | Varies |
| UTC+12:45 | Chatham Islands (New Zealand) | Yes |
| UTC+13:00 | Nuku'alofa (Tonga), Samoa | Varies |
| UTC+14:00 | Kiritimati (Line Islands) | No |
Our 92 Cities by Region
The WhatTimeIsIt.blog city dataset covers 92 major cities across six global regions. The chart below shows how our coverage is distributed — reflecting both population density and international travel and business patterns.
Cities by Region
Countries That Span Multiple Time Zones
While most countries fit within a single time zone, several large nations span multiple offsets — and their choices about whether to unify or divide reveal fascinating national priorities.
| Country | Time Zones Used | Natural Zones | Notes |
|---|---|---|---|
| Russia | 11 | 11 | Largest span: UTC+2 to UTC+12 |
| USA | 6 | 6 | Includes Alaska (UTC−9) and Hawaii (UTC−10) |
| Canada | 6 | 6 | Newfoundland uses UTC−3:30 |
| Australia | 5 | 3 | Some states use half-hour offsets |
| Brazil | 4 | 4 | Western Amazon uses UTC−5 |
| China | 1 | 5 | Entire country uses UTC+8 by decree |
| India | 1 | 2 | Compromise UTC+5:30 half-hour offset |
| France | 12 | 1 | Includes overseas territories worldwide |
How to Convert Between Time Zones
The UTC Offset Method
Converting between time zones is straightforward in principle: find the UTC offset of your source location, find the UTC offset of your destination, and calculate the difference. For example, New York (UTC−5 in winter, UTC−4 in summer) to Tokyo (UTC+9, no DST) is a difference of 14 hours in winter and 13 hours in summer.
The DST Complication
The complication arises from Daylight Saving Time (DST). Not all countries observe it, and those that do change their clocks on different dates. The USA and Canada change on the second Sunday in March and first Sunday in November. Most of Europe changes on the last Sunday in March and last Sunday in October. This means the time difference between, say, New York and London changes three times per year — not just twice.
For reliable conversions, use our Timezone Converter which automatically accounts for DST transitions in real time.
The IANA Time Zone Database
Every operating system, programming language, and time-aware application ultimately relies on the IANA Time Zone Database (also called the Olson database, after its original maintainer Arthur David Olson). This open-source database, maintained at iana.org/time-zones, contains the complete history of every time zone rule change for every territory on Earth — going back to the late 19th century.
The database uses a hierarchical naming convention: Continent/City, such asAmerica/New_York, Europe/London, or Asia/Tokyo. This naming is intentional — cities are more stable identifiers than political entities, which can change names, split, or merge. All time data on WhatTimeIsIt.blog uses IANA timezone identifiers for accuracy and consistency.
Time Zone Changes Coming in 2026
Recent Notable Changes
Time zones are not static. Countries periodically change their rules — sometimes permanently abolishing DST, sometimes shifting their standard offset to align with trading partners. Recent notable changes include:
- Samoa (2011): Crossed the International Date Line to align with Australia and New Zealand, skipping December 30, 2011 entirely.
- Russia (2014): Permanently moved to "permanent summer time," eliminating DST transitions.
- North Korea (2018): Moved from UTC+8:30 back to UTC+9 to align with South Korea.
- European Union: Has been debating abolishing DST since 2018; member states have not yet reached consensus on a final decision.
WhatTimeIsIt.blog updates its time zone data with every IANA database release to ensure all 92 cities always display accurate local time.
Explore Live Time Zones
The best way to understand time zones is to see them live. Browse our city pages to see the current local time, date, weather, and timezone details for cities in every UTC offset: