🌍 Time Zone Converter 2026
Convert time between 50+ cities and time zones worldwide. View live UTC clock, all US time zones (EST, CST, MST, PST, AKST, HST), world clock for 12 major cities with automatic day/night detection, UTC offset reference, DST rules, and time zone math formulas rendered with MathJax. Perfect for scheduling international meetings, flight planning, remote teams, and global trading.
🔄 Time Zone Converter
Convert Time Between Any Two Time Zones
🇺🇸 United States Time Zones — Live
🌏 World Clock — Major Cities
🗺️ UTC Offset Reference Table (2026)
| Time Zone | Abbrev | UTC Offset | DST Offset | Major Cities |
|---|---|---|---|---|
| Hawaii–Aleutian Standard | HST | UTC−10 | No DST (Hawaii) | Honolulu, Hilo |
| Alaska Standard Time | AKST | UTC−9 | AKDT UTC−8 (Mar–Nov) | Anchorage, Fairbanks |
| Pacific Standard Time | PST | UTC−8 | PDT UTC−7 (Mar–Nov) | Los Angeles, Seattle, Vancouver |
| Mountain Standard Time | MST | UTC−7 | MDT UTC−6 (Mar–Nov) | Denver, Calgary · Phoenix (no DST) |
| Central Standard Time | CST | UTC−6 | CDT UTC−5 (Mar–Nov) | Chicago, Dallas, Mexico City |
| Eastern Standard Time | EST | UTC−5 | EDT UTC−4 (Mar–Nov) | New York, Toronto, Miami, Atlanta |
| Atlantic Standard Time | AST | UTC−4 | ADT UTC−3 | Halifax, Puerto Rico, Barbados |
| Brasilia Time | BRT | UTC−3 | BRST UTC−2 (limited states) | São Paulo, Rio de Janeiro, Brasilia |
| Greenwich Mean Time | GMT | UTC+0 | BST UTC+1 (Mar–Oct) | London, Dublin, Lisbon, Reykjavik |
| Central European Time | CET | UTC+1 | CEST UTC+2 (Mar–Oct) | Paris, Berlin, Rome, Madrid, Amsterdam |
| Eastern European Time | EET | UTC+2 | EEST UTC+3 (Mar–Oct) | Athens, Bucharest, Helsinki, Cairo |
| Arabia Standard Time | AST | UTC+3 | No DST | Riyadh, Kuwait, Baghdad, Moscow (MSK) |
| Gulf Standard Time | GST | UTC+4 | No DST | Dubai, Abu Dhabi, Muscat |
| Pakistan Standard Time | PKT | UTC+5 | No DST | Karachi, Lahore, Islamabad |
| India Standard Time | IST | UTC+5:30 | No DST | Mumbai, Delhi, Bangalore, Chennai |
| Nepal Time | NPT | UTC+5:45 | No DST | Kathmandu (unique quarter-hour offset) |
| Bangladesh / Bhutan | BST/BTT | UTC+6 | No DST | Dhaka, Thimphu |
| Indochina / Thailand | ICT | UTC+7 | No DST | Bangkok, Hanoi, Jakarta |
| China / Singapore / HK | CST/SGT/HKT | UTC+8 | No DST | Beijing, Singapore, Hong Kong, Manila, Taipei |
| Japan / Korea | JST/KST | UTC+9 | No DST | Tokyo, Seoul, Osaka, Pyongyang |
| Australian Eastern | AEST | UTC+10 | AEDT UTC+11 (Oct–Apr) | Sydney, Melbourne, Brisbane (no DST) |
| New Zealand | NZST | UTC+12 | NZDT UTC+13 (Sep–Apr) | Auckland, Wellington |
📖 How to Use This Time Zone Converter
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1Read the Live UTC Clock
The purple UTC bar at the top shows the current Coordinated Universal Time, updated every second. It also displays the Unix timestamp (seconds since January 1, 1970 00:00:00 UTC) and ISO 8601 format — used in APIs, databases, and programming.
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2Pick From and To Time Zones
In the converter, select your source time zone (e.g., New York / Eastern) and target time zone (e.g., London / GMT-BST). Use the quick city buttons below each selector for the most common zones. Click ⇄ to swap the two zones.
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3Enter the Date and Time to Convert
The datetime picker defaults to the current time in your browser's local timezone. Adjust to any date and time you need to convert — useful for scheduling future international meetings, checking meeting time across time zones, or verifying a historical timestamp.
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4Read the Converted Time and Copy
The result box shows the converted time in 12-hour and 24-hour formats, date (with day-of-week to catch date-line crossings), and the UTC offset difference. Click "📋 Copy Result" to copy a formatted string to clipboard for pasting into calendar invites or emails.
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5Use the World Clock for Global Team Scheduling
The world clock section shows 12 major cities with live current times, updating every second. City cards appear dark navy for cities currently in nighttime (local hour 8 PM to 6 AM) — instantly showing which team members are sleeping. Use the UTC reference table for the full list of offsets.
📐 Time Zone Conversion — Mathematical Formulas
\( T_B = T_A + (\Delta_B - \Delta_A) \)
\( \text{where } \Delta_X = \text{UTC offset of zone } X \text{ (in hours, signed integer or fraction)} \)
\( \text{Example: } T_A = \text{10:00 AM EST} \Rightarrow \Delta_A = -5 \quad \text{Convert to IST} \Rightarrow \Delta_B = +5.5 \)
\( T_B = 10{:}00 + (+5.5 - (-5)) = 10{:}00 + 10.5\,\text{h} = \mathbf{20{:}30 = 8{:}30\,PM\,IST} \)
\( \text{With DST:} \quad T_B = T_A + (\Delta_B + \text{dst}_B) - (\Delta_A + \text{dst}_A) \)
\( \tau = \text{seconds elapsed since } T_{\text{epoch}} = 1970\text{-}01\text{-}01\;00{:}00{:}00\;\text{UTC} \)
\( T_{\text{UTC}} = T_{\text{epoch}} + \tau\;\text{seconds} \qquad T_{\text{local}} = T_{\text{UTC}} + \Delta_{\text{local}} \)
\( \text{As of April 2026: } \tau \approx 1{,}745{,}000{,}000 \text{ (approximately 1.745 billion seconds)} \)
\( \text{Days since epoch: } \lfloor\tau / 86400\rfloor \approx 20{\,}200 \text{ days} \)
\( \text{ISO 8601: } 2026\text{-}04\text{-}17T01{:}30{:}00\text{+04:00} \quad \Rightarrow \quad \text{date, time, UTC offset encoded together} \)
\( \text{Offset difference} = \Delta_B - \Delta_A \quad \text{positive: } B \text{ is ahead; negative: } B \text{ is behind} \)
\( \text{New York (EST) to Tokyo (JST): } \Delta = +9 - (-5) = +14\,\text{h} \quad \text{(Tokyo is 14h ahead)} \)
\( \text{Dubai (GST) to New York (EDT summer): } \Delta = -4 - (+4) = -8\,\text{h} \quad \text{(NY is 8h behind Dubai)} \)
\( \text{London (GMT) to Los Angeles (PST): } \Delta = -8 - 0 = -8\,\text{h} \quad \text{(LA is 8h behind; 5h in summer)} \)
🕐 The History of Time Zones — From Solar Time to Atomic Clocks
Before the 19th century, every town kept its own local solar time — noon was when the sun was directly overhead. This was perfectly adequate when horses and boats were the fastest transport, but the railways changed everything. When a train travelled from Bristol to London in 2 hours, meeting schedules became impossible: Bristol mean time was 10 minutes behind London time, creating confusion across timetables.
The British railway companies solved this locally by standardising on Greenwich Mean Time (GMT) across their networks in the 1840s. The global solution came at the International Meridian Conference in Washington D.C. in 1884, where 26 countries agreed to establish Greenwich as the prime meridian (0°) and divide the Earth into 24 time zones — one for each hour, each spanning 15 degrees of longitude (since \(360° \div 24 = 15°\)).
However, the perfectly regular 15°-per-zone theory quickly yielded to political reality. Countries wanted their entire territory in one zone for administrative simplicity. China, which geographically spans five 15°-wide zones, uses a single time zone: China Standard Time (UTC+8) — meaning the western province of Xinjiang experiences sunrise as late as 10 AM in winter by the clock. India similarly uses a single zone (IST, UTC+5:30), with the 30-minute offset chosen as a compromise between the zones that would otherwise split the country.
🔬 GMT vs UTC — What's the Difference?
GMT (Greenwich Mean Time) is the mean solar time at the Royal Observatory in Greenwich, London — defined astronomically as the average of all observations of when the sun crosses the meridian (adjusted for Earth's elliptical orbit). It changes slightly with Earth's variable rotation rate and has no sub-second precision.
UTC (Coordinated Universal Time), established in 1960 and standardized by the International Telecommunication Union (ITU-R TF.460-6), is defined by atomic clocks — specifically the International Atomic Time (TAI, from the French Temps Atomique International), which counts the resonant oscillations of cesium-133 atoms at exactly 9,192,631,770 cycles per second. UTC is kept within ±0.9 seconds of mean solar time through the periodic insertion of "leap seconds" (27 have been inserted between 1972 and 2017; none since January 2017).
In practice, for everyday time zone conversion purposes, GMT = UTC. The distinction matters only in precision scientific contexts (GPS satellites, VLBI astronomy, high-frequency trading systems requiring nanosecond accuracy). All modern time zone databases, APIs, and operating systems use UTC as the reference and express local times as UTC offsets.
Half & Quarter Hour Offsets
Not all time zones align to whole hours. India (UTC+5:30), Iran (UTC+3:30), Afghanistan (UTC+4:30), Myanmar (UTC+6:30), and parts of Australia (UTC+9:30 SA, UTC+10:30 Lord Howe) use half-hour offsets. Nepal is unique at UTC+5:45 — the world's only quarter-hour offset, a deliberate 15-minute difference from India to emphasise national identity.
IANA tz Database
Every major operating system (Linux, macOS, Windows, Android, iOS) uses the IANA Time Zone Database (Olson database), maintained at iana.org/time-zones. It contains historical DST rules, zone boundary changes, and political timezone adjustments dating to 1970. This calculator's dropdown uses IANA zone identifiers (e.g., America/New_York) via the browser Intl API.
Global Markets & Time Zones
Financial markets operate in strictly defined time windows: NYSE 9:30 AM–4:00 PM EST · London Stock Exchange 8:00 AM–4:30 PM GMT · Tokyo Stock Exchange 9:00 AM–3:30 PM JST. The "overlap window" (NYSE + LSE simultaneous trading: 9:30–11:30 AM EST / 2:30–4:30 PM GMT) typically sees the highest trading volumes and liquidity in the global forex market.
Aviation & Zulu Time
Aviation universally uses UTC (called "Zulu time" or "Z") for all flight plans, NOTAM (Notices to Airmen), weather reports (METARs, TAFs), and ATC communications. "1430Z" means 14:30 UTC. Military NATO uses the letter-code system: Z=UTC, A=UTC+1 through M=UTC+12 (J skipped), N=UTC−1 through Y=UTC−12. This eliminates all ambiguity across time zones worldwide.
🌅 Daylight Saving Time — Who Uses It and Why?
Daylight Saving Time (DST) — setting clocks forward one hour in spring and back in autumn — is observed by approximately 70 countries including the US, Canada, most of Europe, Australia, and New Zealand. The remaining ~140 countries do not, including all of Africa, most of Asia (including China, Japan, India, and the entire Middle East except Israel and Jordan), most of South America, and the Pacific Islands.
The US instituted DST year-round during World War I (1918) and World War II (1942–1945) to save energy. The modern US DST schedule was extended twice: first by the Energy Policy Act of 1992, then again by the Energy Policy Act of 2005 — which pushed the start to the second Sunday in March and the end to the first Sunday in November (adding approximately 4 weeks of DST compared to the pre-2007 schedule). Arizona (except Navajo Nation), Hawaii, and the US territories of Puerto Rico, Guam, and the US Virgin Islands do not observe DST.
The EU has been considering permanently abolishing DST since a 2019 European Parliament vote (410–192) in favour of elimination. However, implementation has been delayed due to the complex question of which "permanent time" to keep (permanent summer time or permanent standard time), with different member states preferring different options. As of April 2026, the EU still observes seasonal DST changes.