Time Zones
Complete guide to world time zones
What is a Time Zone?
A time zone is a region where the same standard time is used. The world is divided into 24 time zones, based on 15-degree divisions of longitude. Each zone differs from UTC (Coordinated Universal Time) by a set number of hours.
Major Time Zones
| Time Zone | Abbreviation | UTC Offset | Current Time | Major Cities |
|---|---|---|---|---|
| Pacific Standard Time | PST DST | UTC-8 | --:-- | Los Angeles, Seattle, Vancouver |
| Mountain Standard Time | MST DST | UTC-7 | --:-- | Denver, Phoenix, Calgary |
| Central Standard Time | CST DST | UTC-6 | --:-- | Chicago, Dallas, Mexico City |
| Eastern Standard Time | EST DST | UTC-5 | --:-- | New York, Toronto, Miami |
| Greenwich Mean Time | GMT | UTC+0 | --:-- | London, Dublin, Lisbon |
| Central European Time | CET DST | UTC+1 | --:-- | Paris, Berlin, Rome |
| Eastern European Time | EET DST | UTC+2 | --:-- | Athens, Cairo, Istanbul |
| Moscow Standard Time | MSK | UTC+3 | --:-- | Moscow, St. Petersburg |
| Gulf Standard Time | GST | UTC+4 | --:-- | Dubai, Abu Dhabi, Muscat |
| India Standard Time | IST | UTC+5:30 | --:-- | Mumbai, Delhi, Bangalore |
| China Standard Time | CST | UTC+8 | --:-- | Beijing, Shanghai, Hong Kong |
| Japan Standard Time | JST | UTC+9 | --:-- | Tokyo, Osaka, Seoul |
| Australian Eastern Time | AEST DST | UTC+10 | --:-- | Sydney, Melbourne, Brisbane |
| New Zealand Standard Time | NZST DST | UTC+12 | --:-- | Auckland, Wellington |
DST = Observes Daylight Saving Time (offset may vary by 1 hour seasonally)
Related Time Tools
Frequently Asked Questions
The Complete Guide to World Time Zones
Time zones define the standard local time for regions around the world. While the concept sounds simple—divide the globe into 24 slices, one per hour—the reality is far more complex. Political borders, historical decisions, and practical considerations have produced over 30 distinct UTC offsets, including several that use half-hour and even quarter-hour intervals. This guide covers everything you need to know about UTC offsets, unusual time zones, Daylight Saving Time rules, and common abbreviations.
Understanding UTC Offsets
Every time zone is defined by its offset from Coordinated Universal Time (UTC). The offset tells you how many hours (and sometimes minutes) to add or subtract from UTC to get the local time. UTC+0 runs through the United Kingdom, Portugal, Iceland, and several West African nations. As you move east, offsets increase: UTC+1 covers most of Western and Central Europe, UTC+2 covers Eastern Europe and much of the Middle East, and so on up to UTC+12 in New Zealand and some Pacific islands. Moving west from the prime meridian, offsets decrease: UTC-1 covers the Azores and Cape Verde, UTC-5 covers the US Eastern seaboard, and UTC-10 covers Hawaii.
Calculating Time Differences
Time difference = UTC offset of City A − UTC offset of City B
Example: New York (UTC-5) to Dubai (UTC+4)
Difference = (+4) − (−5) = 9 hours
When it is 8:00 AM in New York, it is 5:00 PM in Dubai.
Half-Hour and Quarter-Hour Time Zones
Not all time zones follow whole-hour offsets. Several countries use fractional offsets for political, geographical, or historical reasons:
- India (UTC+5:30): India chose a single half-hour offset to create one unified timezone across the entire country, splitting the difference between its eastern and western extremes.
- Nepal (UTC+5:45): Nepal adopted a quarter-hour offset to distinguish itself from India and to better align with its geographic solar noon.
- Iran (UTC+3:30): Iran uses a half-hour offset that places it between the Gulf states (UTC+4) and Turkey (UTC+3).
- Myanmar (UTC+6:30): Myanmar’s half-hour offset reflects its position between Bangladesh (UTC+6) and Thailand (UTC+7).
- Afghanistan (UTC+4:30): Afghanistan sits between Iran (UTC+3:30) and Pakistan (UTC+5), using its own half-hour offset.
- Chatham Islands (UTC+12:45): This New Zealand territory uses a 45-minute offset from New Zealand Standard Time, making it one of the world’s most unusual time zones.
- Marquesas Islands (UTC-9:30): This French Polynesian territory uses a rare negative half-hour offset.
Unusual Time Zones Around the World
| Location | UTC Offset | Why It’s Unusual |
|---|---|---|
| Nepal | UTC+5:45 | Only country at :45 offset (along with Chatham Islands) |
| Chatham Islands | UTC+12:45 | Furthest ahead in the world during NZ DST (UTC+13:45) |
| Marquesas Islands | UTC-9:30 | Only inhabited region at this offset |
| Line Islands (Kiribati) | UTC+14 | First place to enter a new calendar day |
| China | UTC+8 (single zone) | One timezone for 5 geographical zones; sunrise at 10 AM in western China |
| India | UTC+5:30 | Single timezone for 1.4 billion people across 30° of longitude |
| North Korea | UTC+9 | Switched from UTC+8:30 back to UTC+9 in 2018 |
| Eucla (Australia) | UTC+8:45 | Unofficial; used by a tiny border community |
Daylight Saving Time Rules Worldwide
Daylight Saving Time (DST) is the practice of moving clocks forward by one hour during warmer months to extend evening daylight. About 70 countries observe DST, but they do so on different schedules and some have recently abandoned the practice entirely.
DST by Region
United States & Canada: Spring forward on the second Sunday in March; fall back on the first Sunday in November. Arizona and Hawaii do not observe DST.
European Union: Spring forward on the last Sunday in March; fall back on the last Sunday in October. The EU has debated abolishing DST since 2019, but no final decision has been implemented.
Southern Hemisphere: Australia (except Queensland, NT, and WA) and New Zealand observe DST from October to April—the opposite schedule of the Northern Hemisphere.
Countries that recently abolished DST: Russia (2014), Turkey (2016), Morocco (2018, then adopted permanent DST), and Brazil (2019).
Common Time Zone Abbreviations
| Abbreviation | Full Name | Standard Offset | DST Offset |
|---|---|---|---|
| EST / EDT | Eastern Standard / Daylight | UTC-5 | UTC-4 |
| CST / CDT | Central Standard / Daylight | UTC-6 | UTC-5 |
| MST / MDT | Mountain Standard / Daylight | UTC-7 | UTC-6 |
| PST / PDT | Pacific Standard / Daylight | UTC-8 | UTC-7 |
| GMT / BST | Greenwich Mean / British Summer | UTC+0 | UTC+1 |
| CET / CEST | Central European / Summer | UTC+1 | UTC+2 |
| EET / EEST | Eastern European / Summer | UTC+2 | UTC+3 |
| IST | India Standard Time | UTC+5:30 | N/A |
| JST | Japan Standard Time | UTC+9 | N/A |
| AEST / AEDT | Australian Eastern Standard / Daylight | UTC+10 | UTC+11 |
| NZST / NZDT | New Zealand Standard / Daylight | UTC+12 | UTC+13 |
Ambiguous Abbreviations
Some abbreviations are shared by multiple time zones. “CST” can mean Central Standard Time (UTC-6), China Standard Time (UTC+8), or Cuba Standard Time (UTC-5). “IST” can refer to India Standard Time (UTC+5:30), Irish Standard Time (UTC+1), or Israel Standard Time (UTC+2). When precision matters—in scheduling, programming, or travel—always use the full UTC offset or IANA timezone identifiers (e.g., “America/New_York”) instead of abbreviations.
Tips for Working Across Time Zones
- Always specify the timezone when scheduling meetings or deadlines. “3:00 PM” is meaningless without a timezone qualifier.
- Use UTC for coordination when three or more time zones are involved. Everyone converts from one reference point instead of cross-referencing each other.
- Account for DST transitions. Schedule important events at least one week away from any DST change date to avoid confusion.
- Use the IANA timezone database (also called the Olson database) in software applications. Entries like “Europe/London” or “Asia/Kolkata” automatically handle DST rules and historical changes.
- Check our World Clock to see current times in major cities before scheduling.
Example: Converting Between Unusual Offsets
You are in New York (UTC-5) and need to call Kathmandu, Nepal (UTC+5:45). The difference is 10 hours and 45 minutes. If it is 9:00 AM in New York, it is 7:45 PM in Kathmandu. During US daylight saving time (EDT, UTC-4), the gap shrinks to 9 hours 45 minutes, making your 9:00 AM call land at 6:45 PM in Kathmandu.