World Time Zones Directory & Global Local Time
Explore the complete world time zones directory, UTC standards, Daylight Saving Time schedules, and current local time across 240+ global cities.
How Global Time Zones Work: Longitude, Solar Noon & The 24-Hour Day
Because the Earth rotates 360 degrees on its axis once every 24 hours, solar noon occurs at different moments around the planet (which you can visualize on our Sunrise & Sunset Calculator and World Day & Night Map). In the late 19th century, Sir Sandford Fleming proposed dividing the globe into 24 standard longitudinal zones, each spanning approximately 15 degrees of longitude (360ยฐ / 24 hours = 15ยฐ per hour).
Global time zones are anchored to the Prime Meridian (0ยฐ longitude) running through Greenwich, England, establishing Coordinated Universal Time (UTC) as the baseline. Exactly opposite the Prime Meridian lies the International Date Line in the Pacific Ocean (around 180ยฐ longitude), where calendar dates advance or retreat by 24 hours when crossed.
While geometric time zones are 15 degrees wide, actual civil boundaries follow national and state borders for economic convenience. Some expansive countries like China span five geographical time zones but legally observe a single unified time (China Standard Time, UTC+8). Furthermore, several nations maintain fractional half-hour or 45-minute offsetsโsuch as India (UTC+5:30), Iran (UTC+3:30), and Nepal (UTC+5:45)โto ensure solar noon aligns closely with standard noon. To convert hours between any locations, use the Time Zone Converter, or view live clocks on the World Clock.
What is UTC? (Coordinated Universal Time)
Understand the global primary time standard, why GMT is not identical to UTC, and how atomic clocks regulate global time.
Read UTC Guide โDaylight Saving Time (DST) Explained
How DST works, which countries observe seasonal clock changes, historical origins, and upcoming transition schedules.
Read DST Guide โTime Zone Abbreviations Glossary
Searchable directory of world timezone acronyms including EST, PST, CET, BST, IST, JST, and AEDT with their exact UTC offsets.
Explore Abbreviations โ๐ Global City & Time Zone Directory
North America (36 cities)
Europe (73 cities)
Europe / Asia (7 cities)
Asia (59 cities)
Oceania (14 cities)
South America (17 cities)
Africa (12 cities)
Frequently Asked Questions
Common questions about how world time zones, UTC offsets, and civil boundaries function.
What is a time zone?
A time zone is a geographic region of the globe that observes a uniform standard civil time for legal, commercial, and social purposes.
How do time zones work?
Because Earth rotates 360 degrees in 24 hours, the planet is divided into 24 theoretical longitudinal sections of roughly 15 degrees each. Civil boundaries are adjusted along national and administrative borders, with each zone defining its standard time as an offset from the Prime Meridian.
What is a UTC offset?
A UTC offset is the difference in hours and minutes between a region standard civil time and Coordinated Universal Time (UTC). Offsets range from UTC-12:00 in the western Pacific to UTC+14:00 in the Line Islands.
Why do some time zones have 30-minute or 45-minute offsets?
Several jurisdictionsโsuch as India (UTC+5:30), Iran (UTC+3:30), and Nepal (UTC+5:45)โchose half-hour or 45-minute fractional offsets so that civil time corresponds more naturally with the midpoint of solar noon across their national landmass.
Why do some countries have multiple time zones?
Large countries spanning broad east-to-west geographic distances (such as the United States, Canada, Russia, and Australia) observe multiple time zones so that daylight hours stay roughly aligned with morning and evening civil routines across the nation.
How is local time calculated from UTC?
Local time is calculated by taking the current UTC time and adding the region positive offset (if located east of the Prime Meridian) or subtracting its negative offset (if located west of the Prime Meridian), including any active daylight saving adjustment.
What is daylight saving time?
Daylight Saving Time (DST) is the seasonal practice of advancing clocks by one hour during spring and summer months to extend daylight into civil evening hours, before resetting back to standard time in autumn.
Why do time-zone differences change during the year?
The time difference between two locations changes when one location observes seasonal daylight saving adjustments while the other maintains standard time, or when both observe daylight saving on different transition schedules.