Everything you need to know about how the world tells time. Browse 35 UTC offsets across 250 countries and territories.
Time zones are essential for global communication, travel, and business. This guide explains how time zones work, why they exist, and how daylight saving time affects clocks worldwide. Use the links below to explore specific offsets, see live times in major cities, or convert between any two time zones.
Whether you are scheduling an international meeting, planning a trip, or simply curious about what time it is on the other side of the world, this guide will help you understand the complex but fascinating system that keeps the world synchronized.
A time zone is a region of the globe that observes a uniform standard time for legal, commercial, and social purposes. Time zones tend to follow the boundaries of countries and their subdivisions because it is convenient for areas in close commercial or other communication to keep the same time.
Most time zones on land are offset from Coordinated Universal Time (UTC) by a whole number of hours (UTC−12:00 to UTC+14:00), but a few zones are offset by 30 or 45 minutes, such as India (UTC+5:30), Nepal (UTC+5:45), and parts of Australia (UTC+8:45, UTC+9:30, UTC+10:30).
Before time zones were standardized, each town and city maintained its own local time based on the sun\'s position. This became impractical with the advent of railroads and telegraphs in the 19th century, leading to the adoption of standardized time zones.
Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks. It is not adjusted for daylight saving time and serves as the reference point for all other time zones.
A UTC offset tells you how many hours ahead or behind UTC a particular location is. For example:
The maximum practical time difference between two places on Earth is 26 hours (UTC-12 to UTC+14), though most commonly used offsets range from UTC-11 to UTC+12. Browse all UTC offsets →
Daylight Saving Time is the practice of advancing clocks by one hour during warmer months to extend evening daylight. Not all countries observe DST:
When DST is active, time zone abbreviations change to reflect the new offset:
DST transitions typically occur in March/April (spring forward) and September/November (fall back), though exact dates vary by country and hemisphere. Our live clocks automatically handle these transitions. Check current time in all major zones →
Some countries are so large that a single time zone would create impractical situations where sunrise occurs at midnight or noon. These countries use multiple time zones:
China is a notable exception — despite spanning approximately 5 natural time zones, the entire country uses a single time zone: China Standard Time (UTC+8). This means sunrise in western China can occur as late as 10:00 AM during winter. Explore live world clocks →
The International Date Line (IDL) is an imaginary line on the Earth\'s surface, generally following the 180° meridian, where the date changes as one travels east or west across it. Traveling eastward across the line subtracts one day, while traveling westward adds one day.
This is why some UTC+14 regions (such as Kiribati\'s Line Islands) are technically the first to experience a new calendar day, while UTC-12 regions (Baker Island) are the last. The IDL deviates from the 180° meridian in several places to avoid splitting countries and island groups into two different calendar days.
For travelers crossing the Pacific, the date line can create confusing situations — you can leave Tokyo on Monday morning and arrive in Los Angeles on Sunday morning, effectively "gaining" a day. Conversely, flying the opposite direction can cause you to "lose" a day.
Before the 19th century, each town kept its own local time based on the sun\'s position. This system worked fine when travel was slow, but became chaotic with the expansion of railroads and telegraph networks.
In 1884, the International Meridian Conference in Washington D.C. established the Greenwich Meridian (0° longitude) as the Prime Meridian and divided the world into 24 time zones. This system was gradually adopted worldwide over the following decades.
Daylight Saving Time was first proposed by George Vernon Hudson in 1895 and implemented during World War I to conserve energy. Today, approximately 70 countries observe some form of DST, though the trend in recent years has been toward abolishing it.
A time zone is a region of the globe that observes a uniform standard time for legal, commercial, and social purposes. Time zones are usually offset from Coordinated Universal Time (UTC) by whole hours, though some use 30 or 45 minute offsets.
There are 24 primary time zones corresponding to the 24 hours in a day, but due to political boundaries and fractional offsets, there are approximately 40 different time zones in use worldwide. Some countries span multiple time zones.
UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. All local times are expressed as offsets from UTC. For example, New York is UTC-5, London is UTC+0, and Tokyo is UTC+9.
Daylight Saving Time is the practice of advancing clocks by one hour during warmer months to extend evening daylight. Not all countries observe DST. The start and end dates vary by country and hemisphere.
Large countries like Russia, the United States, Canada, Australia, and Brazil span multiple time zones because they cover vast east-west distances. This ensures local time roughly matches the sun\'s position in the sky.
The International Date Line is an imaginary line on Earth\'s surface, generally following the 180° meridian, where the calendar date changes. Crossing it eastward subtracts a day; crossing westward adds a day.
Find the UTC offset for each city, then subtract the smaller from the larger. The result is the time difference. Use our time converter or meeting planner for instant calculations.
Common abbreviations include EST (UTC-5), PST (UTC-8), GMT (UTC+0), CET (UTC+1), IST (UTC+5:30), JST (UTC+9), and AEST (UTC+10). Note that some abbreviations change during DST (e.g., EST becomes EDT). Check our Time Now page for live clocks in every major zone.
Explore more tools to find time information and plan across time zones: