Timezone Basics
Essential knowledge about time zones, UTC, and how the world keeps time.
What Is a Time Zone?
A time zone is a region of the world that observes a uniform standard time. Learn how time zones were created and why every country …
Understanding UTC — The World's Time Standard
UTC (Coordinated Universal Time) is the basis for all world clocks. Discover what UTC is, how it works, and why it replaced GMT as the …
How Time Zones Work — 24 Zones Explained
Earth is divided into 24 time zones based on longitude. Learn how the system works, how zones are numbered, and why the real map is …
GMT vs UTC — What's the Difference?
GMT and UTC are often used interchangeably, but they are not the same thing. Learn the key differences between Greenwich Mean Time and Coordinated Universal …
International Date Line — Where the Day Changes
The International Date Line is an imaginary line in the Pacific Ocean where the calendar date changes by one day. Learn where it is, why …
Time Zone Map — How the World Is Divided
A look at the world time zone map, why it zigzags along political borders, and which regions have unusual or surprising time zone arrangements.
Half-Hour and Quarter-Hour Time Zones
Not all time zones are whole-hour offsets. India, Nepal, Afghanistan, and others use 30- or 15-minute offsets. Here's why and where these unusual zones exist.
IANA Time Zone Database — The Source of Truth
The IANA Time Zone Database (also called tzdata or the Olson database) is the authoritative reference for time zone rules worldwide. Learn what it is …
Time Zone Abbreviations — EST, PST, JST, KST and More
Time zone abbreviations like EST, GMT, JST, and KST are widely used but often ambiguous. Learn what the most common abbreviations mean and when to …
UTC Offset Explained — What +9, −5 and Others Mean
A UTC offset is the difference between your local time and Coordinated Universal Time. Learn how to read, use, and convert UTC offsets in everyday …
Why Do We Have Time Zones? — History of Railroad Time
Time zones were invented to solve the chaos of hundreds of local times in the railway age. Discover the fascinating history of how the world …
How Many Time Zones Are There? — More Than 24
The world has more than 24 time zones because of political decisions, island territories, and half-hour offsets. Find out the real count and why it …
Countries with Multiple Time Zones — Russia, USA, and More
Some countries span so many degrees of longitude that they use multiple time zones. Russia leads with 11 zones, while the US has 6 and …
Countries That Changed Their Time Zone — Samoa, North Korea, and Others
Countries change their time zones more often than you might think. From Samoa jumping across the date line to North Korea's brief unique offset, here …
Time Zones and the Equator — Why Boundaries Are Irregular
Time zone boundaries should follow straight longitude lines, but geography, politics, and economics make them twist and bend. Learn how the equator and tropics complicate …
Time Zone Boundaries — Political vs Geographic
Time zone boundaries rarely follow neat lines of longitude. They bend around countries, states, and cities for political and economic reasons. Learn how and why.
Military Time Zones — Alpha to Zulu
The military uses a single-letter system to designate time zones from Alpha (UTC+1) to Zulu (UTC+0). Learn the NATO phonetic time zone system and how …
Nautical Time Zones — Maritime Timekeeping
Ships at sea use nautical time zones based on 15-degree longitude bands. Learn how maritime timekeeping works, how it differs from land-based zones, and the …
Time Zones in Space — The ISS Uses UTC
Astronauts on the ISS orbit Earth 16 times a day, making local time meaningless. Learn how the ISS and other spacecraft handle timekeeping, and what …
What Time Is It in Korea? — KST Explained
Korea Standard Time (KST) is UTC+9, with no daylight saving time. Learn the history of KST, how it compares to other major time zones, and …
What Time Is It in Japan? — JST Explained
Japan Standard Time (JST) is UTC+9. Japan has never observed daylight saving time since abandoning it in 1952. Learn about JST, its history, and how …
What Time Is It in China? — One Zone for a Huge Country
China uses a single time zone (CST, UTC+8) across its entire territory despite spanning five geographic zones. Learn why, what challenges this creates, and how …
US Time Zones Explained — Eastern to Hawaii
The contiguous US has four time zones, but including Alaska and Hawaii it has six. Learn the names, offsets, states involved, and daylight saving time …
European Time Zones — CET, EET, and WET
Europe uses three main time zones: WET (UTC+0), CET (UTC+1), and EET (UTC+2). Most of Europe observes daylight saving time, shifting clocks in spring and …
Time Zone FAQs — Common Questions Answered
Answers to the most frequently asked questions about time zones: how to convert them, why clocks change, what UTC means, and more practical time zone …