All timezone abbreviations
Every timezone abbreviation — EST, GMT, CET, CEST, IST, JST and more. Each page shows current time, UTC offset, and all cities in that zone.
North America
Europe
Asia
Africa & Middle East
Australia & Pacific
South America
Complete A–Z list
How time zones work
The modern timezone system was established in the late 19th century to standardize timekeeping for railway schedules and telegraph communication. Before standardized time zones, each city kept its own local solar time, making cross-country scheduling nearly impossible.
Today, time zones are defined relative to Coordinated Universal Time (UTC), which replaced Greenwich Mean Time as the world's time standard in 1972. UTC is maintained by atomic clocks worldwide and serves as the reference point for all civil timekeeping.
Each timezone abbreviation represents a specific offset from UTC. EST (Eastern Standard Time) is UTC−5; during Daylight Saving the Eastern US switches to EDT (UTC−4). Russia spans 11 zones; India uses one for the entire country.
FAQ
What is a timezone abbreviation?
A timezone abbreviation is a short code (usually 2-5 letters) that represents a specific time offset from UTC. For example, EST stands for Eastern Standard Time (UTC-5), GMT for Greenwich Mean Time (UTC+0), and JST for Japan Standard Time (UTC+9). These abbreviations are widely used in scheduling, aviation, and international communication.
What is the difference between UTC and GMT?
UTC (Coordinated Universal Time) and GMT (Greenwich Mean Time) are often used interchangeably, but they differ in definition. GMT is based on mean solar time at Greenwich; UTC is based on atomic clocks. In practice, both have the same time offset (UTC+0), but UTC is the modern scientific standard.
Why do some timezone abbreviations change throughout the year?
Many regions observe Daylight Saving Time (DST), which shifts clocks forward by one hour during warmer months. This creates paired abbreviations like EST/EDT, GMT/BST, and CET/CEST. The switch dates vary by country and hemisphere.
How many time zones are there in the world?
While the Earth is divided into 24 standard hourly time zones, there are actually over 38 unique UTC offsets in use today. India is UTC+5:30, Nepal UTC+5:45. The IANA timezone database tracks over 400 distinct timezone rules when accounting for historical changes.