Convert a date and time between 44 world time zones, with daylight saving applied automatically.
Pick a moment in one zone and read it in another. Daylight saving rules are applied automatically from your browser's own time zone database.
Both lists use IANA zone names, the same database phones, servers and operating systems rely on.
Converted time
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Pick a date, a time and two zones.
To convert a time between two zones, turn the local wall clock reading into a UTC instant by subtracting the source zone's offset, then add the target zone's offset for that same instant. The two offsets have to be looked up for the specific date you are converting, not for today, because most zones move by an hour when daylight saving starts and ends. The converter above does the lookup for you using your browser's own copy of the IANA time zone database, so a meeting on 15 July and the same meeting on 15 January give different answers when either zone observes daylight saving.
UTC instant = local time - source offset target time = UTC instant + target offset 09:00 Toronto (UTC-4) = 13:00 UTC = 14:00 London (UTC+1)A time zone converter answers one narrow question precisely: if it is a particular clock time in one place, what does the clock read in another place at that same moment? That sounds trivial and it is not, because the answer depends on three things that all move. The offset of the source zone from UTC moves twice a year in most of Europe, North America, Australia and New Zealand. The offset of the target zone moves too, on different dates. And the calendar date in the target zone may be a day ahead or a day behind, which is where most missed meetings actually come from.
The tool at the top of this page takes four inputs: a date, a time, a source zone and a target zone. Both dropdowns hold 44 IANA zone identifiers covering Canada and the United States, Latin America, Europe, Africa, the Middle East, South and East Asia, Australia and the Pacific, plus UTC itself. From those four inputs it returns:
UTC+05:30 or UTC-04:00, each with the zone abbreviation your browser reports;Everything runs locally. No date you type is sent anywhere, and once the page has loaded it keeps working with the connection off. If you want the length of a span rather than a conversion of an instant, the Time Duration Calculator measures the gap between two times. If you are working in the 24-hour notation used in aviation and healthcare, the Military Time Converter handles that format, including the Zulu suffix that means UTC.
India runs a single zone across roughly 3,000 km of longitude. The 26-hour spread exists because Kiribati's Line Islands sit at UTC+14 while Baker Island sits at UTC-12, which is why three different dates coexist for two hours out of every twenty-four.
Four inputs, one result. The only judgement call you have to make is which zone the time you were given actually belongs to.
The date matters as much as the time. Type the calendar date of the event in the source zone, then the wall clock reading people in that zone would see. The "Use the current time" button fills in both from your own device.
Choose the zone the clock reading belongs to, not the zone you happen to be sitting in. If a colleague in Berlin said "three o'clock", the source zone is Berlin even if you are reading the message in Halifax.
Select the target zone. Both lists use IANA identifiers such as America/Toronto and Asia/Kolkata, which pin down a whole history of offset rules rather than a single abbreviation.
The large figure is the converted 24-hour time. Check the "Date there" cell before you send anything: a call at 17:00 in New York is 09:00 the following morning in Sydney, and writing the wrong date is the most expensive mistake on this page.
A converter with no date field is guessing. Toronto to London is five hours for most of the year but four hours for about three weeks each March and one week each autumn. Without a date the tool cannot know which applies.
Your browser ships the IANA time zone database and updates it with the browser itself. When a country changes its rules, as Mexico did in 2022 and Egypt did in 2023, the converter follows without any change to this page.
Which zone a written time belongs to. "Thursday at 4" in an email is ambiguous until somebody names a city or an offset. Always ask, and always reply with the zone attached.
Every time zone on Earth is defined as a fixed number of hours and minutes away from one shared reference. Get the reference right and the arithmetic is easy.
Coordinated Universal Time, written UTC, is the time standard the whole world measures against. It is maintained from a weighted average of several hundred atomic clocks held at national laboratories, then nudged with leap seconds so that it never drifts more than 0.9 seconds away from the rotation of the Earth. UTC has no daylight saving, never shifts, and is the same everywhere at once. Twenty-seven leap seconds have been inserted since the system began in 1972, the most recent at the end of December 2016, which is why atomic time (TAI) currently runs 37 seconds ahead of UTC.
A time zone is then just an instruction: take UTC and add or subtract this much. Toronto in winter says "subtract five hours". Delhi says "add five hours and thirty minutes", all year. Auckland in the southern summer says "add thirteen hours". That instruction is the offset, and it is the only thing that separates one zone from another.
local time = UTC + offset UTC = local time - offset Toronto, 15 January: UTC-05:00 14:00 UTC = 09:00 local Toronto, 15 July: UTC-04:00 14:00 UTC = 10:00 local Delhi, any date: UTC+05:30 14:00 UTC = 19:30 local
People use GMT and UTC as if they were interchangeable, and in casual conversation the error is usually harmless because the two agree to within a second. They are not the same thing though, and the difference occasionally matters.
Greenwich Mean Time began as mean solar time at the Royal Observatory in Greenwich: a measurement of where the sun actually is relative to a particular meridian. It is astronomical, tied to the wobbling and gradually slowing rotation of the planet. UTC is atomic, tied to caesium transitions, and only kept in step with the Earth by the occasional leap second. When a scientist says UT1 they mean the modern successor to that astronomical measure, and UT1 and UTC can differ by up to 0.9 seconds at any moment.
In everyday use there is a second, more practical difference. GMT is also the name of a time zone: the one the United Kingdom, Ireland and Portugal use in winter. That zone switches to British Summer Time or Western European Summer Time in the warmer months, so "GMT" as people use it is a zone that stops being GMT for seven months of the year. UTC never does that. If you write a deadline as "23:59 GMT on 30 June" you have written something ambiguous, because in June London is not on GMT at all. Write "23:59 UTC" and there is nothing to argue about.
A UTC offset is not a time zone. UTC-05:00 tells you what a clock reads right now. It does not tell you whether that clock will still read UTC-05:00 next month. Toronto, Bogota, Lima and Havana can all sit at UTC-05:00 on the same winter day and then diverge in spring, because Toronto and Havana move to daylight saving and Bogota and Lima do not. Store the zone, not the offset.
Offsets are written with a sign, two digits of hours, a colon and two digits of minutes: UTC+09:00, UTC-03:30, UTC+05:45. A positive sign means ahead of UTC, so the clock there reads later than in London in winter. A negative sign means behind. The extremes currently in use run from UTC-12:00 in the uninhabited Baker and Howland Islands to UTC+14:00 in the Line Islands of Kiribati, a total spread of 26 hours across a planet that only turns once in 24. That extra two hours exists because a handful of Pacific nations moved themselves across the International Date Line for commercial reasons.
In ISO 8601, the format used by nearly every computer system, the offset is glued onto the end of the timestamp: 2026-07-15T09:00:00-04:00 means nine in the morning at a place that was four hours behind UTC on that date. A trailing Z, spoken "Zulu", means UTC exactly. If you ever have to hand a time to another system, hand it over in that form and the ambiguity disappears. The Date Calculator works in the same ISO date format for the calendar half of the problem.
The converter's dropdowns are populated with names like America/St_Johns rather than NST. That choice is the difference between a tool that is right and one that is right most of the time.
The IANA time zone database, also called the tz database or the Olson database after its original maintainer, is the shared reference that phones, servers, operating systems and browsers all use. It records not just the current offset of every inhabited region on Earth but the full history of that region's offset changes, going back to the point where local mean time gave way to standard time. It is updated several times a year, because governments keep changing their minds.
Entries are named Area/Location, where the area is a continent or ocean and the location is usually the largest city in the region that has shared identical clock rules since 1970. So the zone that covers Ontario and most of the eastern United States is America/Toronto or its long-standing sibling America/New_York. The zone covering all of India is Asia/Kolkata. The zone covering mainland China, all of it, on one offset, is Asia/Shanghai.
America/Mexico_City kept its name and changed its rules.There is one more wrinkle worth knowing. The abbreviation your browser reports for a zone is generated from locale data, not from the IANA database, and it is not always the abbreviation a local would use. Ask for the short zone name of Asia/Kolkata in an English locale and many browsers return GMT+5:30 rather than IST, because the locale data has no widely agreed English abbreviation for that zone. That is a display quirk, not an error: the offset is still exactly right, and the offset is what the arithmetic uses.
The converter shows the abbreviation in brackets after each offset for convenience, but treat the numeric offset as the authoritative half of that cell. If you are writing something down for another person, write the offset. If you are writing something down for another computer, write the IANA identifier or a full ISO 8601 timestamp.
Every zone in the converter's dropdowns, with its standard offset, its daylight offset where one exists, and whether the clocks actually move. Offsets are correct as of 2026.
| Zone and main cities | IANA identifier | Standard | Daylight | DST observed |
|---|---|---|---|---|
| Coordinated Universal Time | UTC | UTC+00:00 | none | No, never |
| Newfoundland (St. John's) | America/St_Johns | UTC-03:30 | UTC-02:30 | Yes (NST to NDT) |
| Atlantic (Halifax, Moncton) | America/Halifax | UTC-04:00 | UTC-03:00 | Yes (AST to ADT) |
| Eastern (Toronto, New York) | America/Toronto | UTC-05:00 | UTC-04:00 | Yes (EST to EDT) |
| Central (Chicago, Winnipeg) | America/Chicago | UTC-06:00 | UTC-05:00 | Yes (CST to CDT) |
| Mountain (Denver, Edmonton) | America/Denver | UTC-07:00 | UTC-06:00 | Yes (MST to MDT) |
| Arizona (Phoenix) | America/Phoenix | UTC-07:00 | none | No exception |
| Pacific (Vancouver, Los Angeles) | America/Vancouver | UTC-08:00 | UTC-07:00 | Yes (PST to PDT) |
| Alaska (Anchorage) | America/Anchorage | UTC-09:00 | UTC-08:00 | Yes (AKST to AKDT) |
| Hawaii (Honolulu) | Pacific/Honolulu | UTC-10:00 | none | No exception |
| Mexico City | America/Mexico_City | UTC-06:00 | none | No, abolished in 2022 |
| Bogota, Lima, Quito | America/Bogota | UTC-05:00 | none | No |
| Sao Paulo, Rio de Janeiro | America/Sao_Paulo | UTC-03:00 | none | No, abolished in 2019 |
| Buenos Aires | America/Argentina/Buenos_Aires | UTC-03:00 | none | No |
| London, Dublin | Europe/London | UTC+00:00 | UTC+01:00 | Yes (GMT to BST) |
| Lisbon | Europe/Lisbon | UTC+00:00 | UTC+01:00 | Yes (WET to WEST) |
| Paris, Madrid, Rome | Europe/Paris | UTC+01:00 | UTC+02:00 | Yes (CET to CEST) |
| Berlin, Amsterdam, Oslo | Europe/Berlin | UTC+01:00 | UTC+02:00 | Yes (CET to CEST) |
| Warsaw, Stockholm, Prague | Europe/Warsaw | UTC+01:00 | UTC+02:00 | Yes (CET to CEST) |
| Athens, Helsinki, Bucharest | Europe/Athens | UTC+02:00 | UTC+03:00 | Yes (EET to EEST) |
| Istanbul | Europe/Istanbul | UTC+03:00 | none | No, fixed since 2016 |
| Moscow, St Petersburg | Europe/Moscow | UTC+03:00 | none | No, fixed since 2014 |
| Lagos, Algiers, Kinshasa | Africa/Lagos | UTC+01:00 | none | No |
| Cairo | Africa/Cairo | UTC+02:00 | UTC+03:00 | Yes, reinstated in 2023 |
| Johannesburg, Harare | Africa/Johannesburg | UTC+02:00 | none | No |
| Nairobi, Addis Ababa | Africa/Nairobi | UTC+03:00 | none | No |
| Jerusalem, Tel Aviv | Asia/Jerusalem | UTC+02:00 | UTC+03:00 | Yes (IST to IDT) |
| Dubai, Abu Dhabi, Muscat | Asia/Dubai | UTC+04:00 | none | No |
| Karachi, Lahore, Islamabad | Asia/Karachi | UTC+05:00 | none | No |
| India (Delhi, Mumbai, Bengaluru) | Asia/Kolkata | UTC+05:30 | none | No half hour |
| Kathmandu | Asia/Kathmandu | UTC+05:45 | none | No quarter hour |
| Dhaka | Asia/Dhaka | UTC+06:00 | none | No |
| Bangkok, Jakarta, Hanoi | Asia/Bangkok | UTC+07:00 | none | No |
| China (Beijing, Shanghai) | Asia/Shanghai | UTC+08:00 | none | No, one zone nationwide |
| Hong Kong, Macau | Asia/Hong_Kong | UTC+08:00 | none | No |
| Singapore, Kuala Lumpur | Asia/Singapore | UTC+08:00 | none | No |
| Seoul | Asia/Seoul | UTC+09:00 | none | No |
| Tokyo, Osaka | Asia/Tokyo | UTC+09:00 | none | No |
| Perth | Australia/Perth | UTC+08:00 | none | No |
| Adelaide | Australia/Adelaide | UTC+09:30 | UTC+10:30 | Yes half hour |
| Brisbane | Australia/Brisbane | UTC+10:00 | none | No exception |
| Sydney, Melbourne, Canberra | Australia/Sydney | UTC+10:00 | UTC+11:00 | Yes (AEST to AEDT) |
| Auckland, Wellington | Pacific/Auckland | UTC+12:00 | UTC+13:00 | Yes (NZST to NZDT) |
| Fiji (Suva) | Pacific/Fiji | UTC+12:00 | none | No, suspended since 2021 |
Daylight offsets are shown only for zones that currently observe daylight saving. Several entries cover more places than the listed cities: America/Toronto and America/New_York keep identical clocks, as do Europe/Berlin, Europe/Paris and every other Central European Time capital. Brisbane and Queensland famously voted against daylight saving and remain on UTC+10:00 all year while Sydney, an hour's flight south, moves to UTC+11:00 each October.
Canada has six time zones and two of them behave unusually. Newfoundland sits at UTC-03:30, thirty minutes off every neighbour. Saskatchewan stays on UTC-06:00 all year, so in summer its clocks match Alberta and in winter they match Manitoba, and it never changes them. Yukon moved to a permanent UTC-07:00 in 2020, so it no longer switches either. Lloydminster, which straddles the Alberta and Saskatchewan border, follows Mountain Time with daylight saving on both sides of the street.
Three letters are not enough to identify a point on the planet. Several of the most commonly used abbreviations refer to zones on opposite sides of the world.
Zone abbreviations are conventions, not standards. No international body assigns them, no register prevents collisions, and different countries picked the same letters for entirely different offsets. The result is that a message reading "the call is at 14:00 CST" is genuinely ambiguous by fourteen hours, and no amount of careful reading will resolve it. The table below lists the abbreviations that most often cause real trouble.
| Code | Competing meanings | Offsets involved | Worst-case error | How dangerous |
|---|---|---|---|---|
| CST | US and Canadian Central Standard Time, China Standard Time, Cuba Standard Time | -06:00, +08:00, -05:00 | 14 h | Avoid entirely |
| IST | India Standard Time, Irish Standard Time, Israel Standard Time | +05:30, +01:00, +02:00 | 4.5 h | Avoid entirely |
| BST | British Summer Time, Bangladesh Standard Time, Bougainville Standard Time | +01:00, +06:00, +11:00 | 10 h | Avoid entirely |
| AST | Atlantic Standard Time (Halifax), Arabia Standard Time (Riyadh) | -04:00, +03:00 | 7 h | Risky |
| WST | Western Standard Time (Perth), West Samoa Time (Apia) | +08:00, +13:00 | 5 h | Risky |
| GST | Gulf Standard Time (Dubai), South Georgia Time | +04:00, -02:00 | 6 h | Risky |
| AMT | Amazon Time (Manaus), Armenia Time (Yerevan) | -04:00, +04:00 | 8 h | Risky |
| EST | North American Eastern Standard Time, Australian Eastern Standard Time (written EST locally) | -05:00, +10:00 | 15 h | Risky |
| PST | Pacific Standard Time (Los Angeles), Philippine Standard Time (informal use) | -08:00, +08:00 | 16 h | Risky |
| CDT | Central Daylight Time (Chicago), Cuba Daylight Time (Havana) | -05:00, -04:00 | 1 h | Check the country |
| ECT | Ecuador Time, and "European Central Time" in some older software | -05:00, +01:00 | 6 h | Check the country |
| MST | Mountain Standard Time (Denver), Myanmar Standard Time (informal use) | -07:00, +06:30 | 13.5 h | Check the country |
| CET, CEST | Central European Time and its summer form only | +01:00, +02:00 | none | Unambiguous |
| UTC, Z | Coordinated Universal Time only | +00:00 | none | Always safe |
The worst-case error column is the largest gap between two live readings of the same code. CST is the standout: read as US Central it is UTC-06:00, read as China Standard Time it is UTC+08:00, and a meeting scheduled on the wrong reading lands fourteen hours away, on a different calendar day. Cuba adds a third reading at UTC-05:00. If you need three letters at all, write the offset beside them.
"Thursday 16 April, 14:00 in Toronto (UTC-4)". A city and an offset together are unambiguous to any reader anywhere, and the offset survives being pasted into another message.
"18:00 UTC on 16 April 2026". Contract deadlines, submission cut-offs and maintenance windows should be written in UTC, because UTC is the one label that means the same thing to every reader in every month.
Store 2026-04-16T18:00:00Z plus the IANA identifier of the zone the event belongs to. Storing only an offset loses the daylight saving rules, and storing only local time loses everything.
The difference between two cities is not a constant. It is a function of the date, and for a few weeks each year it takes a value that surprises people who thought they knew it.
Roughly seventy countries move their clocks forward in spring and back in autumn. The problem for anyone converting times is not that they do it, but that they do it on different dates from each other. Between the earliest and latest transition dates there are windows, some a single week long, in which the familiar gap between two cities is simply wrong.
| Region | Clocks go forward | Clocks go back | Shift | Switch moment |
|---|---|---|---|---|
| United States and Canada (most) | Second Sunday in March | First Sunday in November | +1 h | 02:00 local, so zones move one after another |
| European Union and United Kingdom | Last Sunday in March | Last Sunday in October | +1 h | 01:00 UTC, so the whole bloc moves at the same instant |
| Australia (NSW, VIC, SA, TAS, ACT) | First Sunday in October | First Sunday in April | +1 h | 02:00 local |
| New Zealand | Last Sunday in September | First Sunday in April | +1 h | 02:00 local |
| Lord Howe Island, Australia | First Sunday in October | First Sunday in April | +30 min | 02:00 local, the only half-hour shift on Earth |
| Israel | Friday before the last Sunday in March | Last Sunday in October | +1 h | 02:00 local |
| Egypt | Last Friday in April | Last Thursday in October | +1 h | Reinstated in 2023 after eight years without |
| Chile (mainland) | Early September | Early April | +1 h | Southern hemisphere pattern, dates set by decree |
| Mexico | Not observed | Not observed | 0 | Abolished nationwide in October 2022 |
| Brazil | Not observed | Not observed | 0 | Abolished in 2019 |
| Most of Asia and Africa | Not observed | Not observed | 0 | China, India, Japan, Korea, most African states |
| Arizona, Saskatchewan, Yukon, Queensland | Not observed | Not observed | 0 | Regional opt-outs inside countries that do observe |
Because the European Union switches at a single UTC instant while North America switches at 02:00 in each local zone, the European transition is tidier: every EU country changes together, and no two of them ever disagree. North American zones change over a three and a half hour span, which is invisible to most people but matters to anything logging timestamps.
Take Toronto and London, a pair that millions of people convert between every day. The familiar answer is that London is five hours ahead. That answer is correct for about forty-eight weeks of the year and wrong for four.
Toronto to London in 2026 1 Jan to 8 Mar Toronto UTC-5, London UTC+0 London is 5 h ahead 8 Mar to 29 Mar Toronto UTC-4, London UTC+0 London is 4 h ahead 29 Mar to 25 Oct Toronto UTC-4, London UTC+1 London is 5 h ahead 25 Oct to 1 Nov Toronto UTC-4, London UTC+0 London is 4 h ahead 1 Nov to 31 Dec Toronto UTC-5, London UTC+0 London is 5 h ahead
North America springs forward three weeks before Europe does, and Europe falls back one week before North America does. In both windows the gap narrows to four hours, which means a recurring meeting anchored to Toronto time appears to move an hour earlier for the London participants, and a meeting anchored to London time appears to move an hour later for the Toronto participants. Neither side changed anything. Only the calendar did.
Australia and New Zealand put their clocks forward in October and back in April, exactly opposite to the northern pattern. When New York gains an hour, Sydney is about to lose one. The two shifts compound rather than cancel, so the New York to Sydney gap moves through three different values in a single year.
New York to Sydney in 2026 1 Jan to 8 Mar New York UTC-5, Sydney UTC+11 Sydney is 16 h ahead 8 Mar to 5 Apr New York UTC-4, Sydney UTC+11 Sydney is 15 h ahead 5 Apr to 4 Oct New York UTC-4, Sydney UTC+10 Sydney is 14 h ahead 4 Oct to 1 Nov New York UTC-4, Sydney UTC+11 Sydney is 15 h ahead 1 Nov to 31 Dec New York UTC-5, Sydney UTC+11 Sydney is 16 h ahead
Anyone who memorises "Sydney is sixteen hours ahead" will be an hour or two out for more than half the year. This is exactly the kind of thing a converter with a date field is for, and it is why the tool at the top of this page asks for the date before it asks for anything else. For counting down to a fixed moment across these boundaries, the Countdown Timer works from a single instant rather than a wall clock reading.
On the morning a region springs forward, one hour of local time does not exist. In Toronto on 8 March 2026 the clocks jump from 01:59:59 to 03:00:00, so there is no such thing as 02:30 that day. On the morning it falls back, one hour happens twice: on 1 November 2026 the hour from 01:00 to 02:00 runs, then runs again. A timestamp of "01:30 local" on that date describes two different instants an hour apart.
Converters and calendar systems have to make a decision about these. The usual convention, and the one this tool follows, is to resolve a non-existent time forward into the hour that does exist, and to resolve a repeated time to its first occurrence. That is a reasonable default, but the honest advice is not to schedule anything at 02:00 to 03:00 local on a transition Sunday. Airlines, hospitals and payroll systems all avoid that window deliberately. If you are totalling shift hours across one of these nights, note that the day itself is 23 or 25 hours long, and the Hours Calculator counts the actual elapsed time rather than the clock difference.
Most of the world sits on a whole hour. A meaningful minority does not, and every piece of software that assumed otherwise has eventually been embarrassed by it.
There is no rule that a time zone must be an integer number of hours from UTC. Standard time was adopted country by country, and several countries chose an offset that matched their solar noon more closely than the nearest hour would have. India, Iran, Afghanistan, Myanmar, Nepal, Newfoundland, central Australia and the Chatham Islands all sit on a thirty or forty-five minute boundary, and between them they cover well over a billion people.
| Place | IANA identifier | Standard | Daylight | Notes |
|---|---|---|---|---|
| India | Asia/Kolkata | UTC+05:30 | none | A single zone for the entire country, roughly 3,000 km wide. No daylight saving has been used since 1945. |
| Sri Lanka | Asia/Colombo | UTC+05:30 | none | Matches India after several changes between 1996 and 2006. |
| Nepal | Asia/Kathmandu | UTC+05:45 | none | Fifteen minutes ahead of India, set to Kathmandu's own solar time. |
| Newfoundland and Labrador (island) | America/St_Johns | UTC-03:30 | UTC-02:30 | Canada's only half-hour zone. Labrador's mainland south coast follows it; the rest of Labrador is on Atlantic Time. |
| Iran | Asia/Tehran | UTC+03:30 | none | Daylight saving abolished in 2022, so the offset is now fixed. |
| Afghanistan | Asia/Kabul | UTC+04:30 | none | Thirty minutes ahead of Iran and thirty minutes behind Pakistan. |
| Myanmar | Asia/Yangon | UTC+06:30 | none | Sits between Bangladesh at UTC+06:00 and Thailand at UTC+07:00. |
| Cocos (Keeling) Islands | Indian/Cocos | UTC+06:30 | none | An Australian external territory that does not use any Australian offset. |
| South Australia, Northern Territory | Australia/Adelaide, Australia/Darwin | UTC+09:30 | UTC+10:30 | Adelaide observes daylight saving, Darwin does not, so they separate for six months a year. |
| Marquesas Islands | Pacific/Marquesas | UTC-09:30 | none | Thirty minutes ahead of the rest of French Polynesia. |
| Lord Howe Island | Australia/Lord_Howe | UTC+10:30 | UTC+11:00 | The only place on Earth whose daylight saving shift is thirty minutes rather than a full hour. |
| Chatham Islands | Pacific/Chatham | UTC+12:45 | UTC+13:45 | Forty-five minutes ahead of New Zealand, and it does observe daylight saving. |
| Eucla, Western Australia | Australia/Eucla | UTC+08:45 | none | An unofficial local arrangement used by a few hundred people on the Nullarbor. |
Fractional offsets are the reason the converter reports the difference between two zones as a decimal. Toronto to Delhi in July is 9.5 hours, London to Kathmandu in January is 5.75 hours, and Adelaide to Auckland in the southern summer is 1.5 hours. Rounding any of those to a whole number produces a wrong answer, and the arithmetic behind the decimal is the same conversion the Decimal Hours Converter performs on durations.
The practical consequence of a forty-five minute offset is that a meeting on the hour in one place is at a quarter past or a quarter to in another. A 10:00 call in London during January is 15:45 in Kathmandu. A 09:00 call in Auckland is 09:45 on the Chathams. There is nothing exotic about this arithmetic, but it defeats the mental shortcut of "just add five", which is how most people convert times in their head and how most of them get it wrong.
The strip of offsets, one instant seen from four cities, and the way a single city pair's gap moves across a year.
Somewhere on the planet the calendar has to change. That line is not straight, is not a treaty, and has been moved for commercial convenience more than once.
If you walk east around the world you gain an hour for every fifteen degrees of longitude, and after a full circuit you would be a day ahead of where you started. The International Date Line is the compensating seam: cross it going west and the calendar jumps forward a day, cross it going east and it jumps back. It roughly follows the 180th meridian in the middle of the Pacific, but it bends substantially, because no country wants to have two dates inside its own borders.
The line is not defined by any international agreement. It is simply the sum of the offset choices each country has made, and countries change those choices. Samoa moved from UTC-11 to UTC+13 at the end of 2011 to align its working week with Australia and New Zealand rather than the United States, and in doing so skipped 30 December 2011 altogether: the country went to bed on Thursday the 29th and woke up on Saturday the 31st. Kiribati made a similar move in 1995, pushing its eastern islands from UTC-10 to UTC+14 so the whole nation would share one date.
Widest live spread of local time Kiribati, Line Islands UTC+14:00 Baker Island (uninhabited) UTC-12:00 --------- total spread 26 hours When UTC reads 10:00 to 11:59 on any given day, three different calendar dates are in use at once.
That two-hour window each day is the reason a global system can never assume that "today" means the same thing to all its users. For roughly two hours out of every twenty-four, somewhere on Earth it is still yesterday, somewhere it is today, and somewhere it is already tomorrow. Anything that generates a daily report, expires a coupon at midnight or closes a voting window has to pick a zone and say so.
A westbound flight from North America to Asia crosses the date line and loses a calendar day. Leave Toronto on a Friday afternoon and you land in Tokyo on Saturday afternoon, even though you were in the air for less than fourteen hours. Coming back the other way you gain the day: leave Tokyo on a Monday morning and land in Toronto on Monday morning, apparently before you took off.
Nothing strange has happened to the duration of the flight. The elapsed time is whatever the schedule says, and that never changes. Only the label on the moment changes. If you want the elapsed time rather than the arrival clock reading, work in UTC from end to end and use the Time Duration Calculator, which measures spans without the zone labels getting in the way.
Neighbouring islands can be a full day apart. American Samoa is on UTC-11 and Samoa is on UTC+13, roughly 130 km away across the water. The clocks read the same hour but the calendars are 24 hours apart, so a Tuesday morning phone call from one is a Wednesday morning call to the other. This is the extreme case of the thing the converter's "Date there" field exists to catch.
The real question is rarely "what time is it there". It is "what hours do we both have available", and for some pairs of cities the honest answer is none.
Take a standard working day of 09:00 to 17:00 in each city and overlay the two. What remains is the overlap window, and it is the only period in which a meeting inconveniences nobody. The table below gives the overlap for eleven common city pairs, in January and in July, because the answer changes with the season.
| City pair | Gap in January | Gap in July | Shared hours | Slot that works |
|---|---|---|---|---|
| St. John's and Toronto | 1.5 h | 1.5 h | 6.5 h | Toronto 09:00 to 15:30 = St. John's 10:30 to 17:00 |
| Toronto and Vancouver | 3 h | 3 h | 5 h | Toronto 12:00 to 17:00 = Vancouver 09:00 to 14:00 |
| Chicago and Sao Paulo | 3 h | 2 h | 5 h to 6 h | Chicago 09:00 to 14:00 = Sao Paulo 12:00 to 17:00 in January |
| London and Dubai | 4 h | 3 h | 4 h to 5 h | London 09:00 to 13:00 = Dubai 13:00 to 17:00 in January |
| Toronto and London | 5 h | 5 h | 3 h | Toronto 09:00 to 12:00 = London 14:00 to 17:00 |
| London and Mumbai | 5.5 h | 4.5 h | 2.5 h to 3.5 h | London 09:00 to 11:30 = Mumbai 14:30 to 17:00 in January |
| Toronto and Berlin | 6 h | 6 h | 2 h | Toronto 09:00 to 11:00 = Berlin 15:00 to 17:00 |
| Vancouver and London | 8 h | 8 h | none | Nearest touch: Vancouver 08:00 = London 16:00 |
| London and Sydney | 11 h | 9 h | none | London 07:00 = Sydney 18:00 in January |
| New York and Sydney | 16 h | 14 h | none | New York 17:00 = Sydney 09:00 next day in January |
| San Francisco and Tokyo | 17 h | 16 h | none | San Francisco 16:00 = Tokyo 09:00 next day in January |
Gaps are for standard working weeks in the given month. Note that the transpacific and Europe to Australia pairs have no genuine overlap at all: somebody is always meeting outside their normal day, and the only fair arrangement is to alternate which side takes the inconvenience. Note also that the working week itself is not universal, and several Gulf states moved from a Sunday to Thursday week to a Monday to Friday week in 2022.
Pick a single zone as the canonical one for the meeting and write it in the invitation title, such as "Sprint review, 14:00 Europe/Berlin". Everyone else converts from that, and there is only ever one number to argue about.
Whenever the gap exceeds about eight hours, at least one participant is on a different calendar day. Writing "Tue 14 April, 22:00 UTC" costs four extra characters and removes the single most expensive class of error.
Those are the four months in which somebody's clocks move. A recurring series anchored to one city's local time will silently shift for everyone else, and nobody gets a notification about it.
Do not schedule anything between 01:00 and 03:00 local on the second Sunday in March, the last Sunday in March, the last Sunday in October or the first Sunday in November. One of those hours does not exist and another happens twice.
For a San Francisco to Tokyo or London to Sydney team there is no fair slot. Alternate weekly between an early call for one side and a late call for the other, and write the rotation down so nobody has to remember whose turn it is.
Calendar files carry the zone with them and recalculate on each device. A time typed into a chat message does not. If a meeting matters, it belongs in a calendar entry with a real time zone attached.
One more piece of arithmetic worth doing before you commit to a schedule: work out the total weekly cost of the inconvenience. A team of four in Vancouver joining a 07:00 call three times a week is giving up three hours of morning per person per week, which is 12 hours across the team. The Hours Calculator will total that quickly, and seeing the number often changes the decision.
Each of these is reproducible in the converter above. The working goes through UTC every time, which is the only method that never fails.
A call is set for 09:00 on Tuesday 14 July 2026 in Toronto. What time is it in London?
= 14:00 (2:00 PM) Tuesday 14 July, London
A standup at 08:30 on Wednesday 15 July 2026 in Vancouver, with people in Toronto, London and Bengaluru.
08:30 Vancouver = 11:30 Toronto = 16:30 London = 21:00 Bengaluru
Depart Toronto Friday 10 July 2026 at 13:25, flight time 13 h 20 min, arriving Tokyo.
Lands 15:45 (3:45 PM) Saturday 11 July, Tokyo
A weekly call at 10:00 Toronto every Monday. What do the London participants see on 16 March 2026?
London sees the call move to 14:00 for three weeks, then back to 15:00
New York wants a standing call that lands at 09:00 in Sydney. What New York time achieves that in January, and in July?
17:00 New York in January, 19:00 New York in July
Applications close at 23:59 UTC on 30 June 2026. When is that locally?
16:59 Vancouver, 19:59 Toronto, 00:59 next day London, 11:59 next day Auckland
Almost every missed international meeting traces back to one of these eight errors. None of them is complicated, which is exactly why they keep happening.
| Mistake | What actually happens | Typical error | The fix |
|---|---|---|---|
| Using a memorised gap | "London is five hours ahead" is right for forty-eight weeks and wrong for four, because the two regions change clocks on different dates. | 1 h | Convert with the actual date every time, especially in March, April, October and November. |
| Writing a bare abbreviation | CST, IST, BST and AST each name at least two live zones. The reader picks the wrong one and joins at the wrong hour. | 1 h to 14 h | Write the city and the numeric offset, or write UTC. |
| Ignoring the calendar date | Any gap above about eight hours puts someone on a different day. The time is right and the day is wrong, so nobody turns up. | 24 h | Always state the date alongside the time, in both zones if the gap is large. |
| Assuming a whole-hour offset | India, Nepal, Newfoundland, Iran, Afghanistan, Myanmar, central Australia and the Chathams are all on a fraction of an hour. | 30 or 45 min | Read the offset from the converter rather than rounding to the nearest hour in your head. |
| Assuming the whole country switches | Arizona, Saskatchewan, Yukon, Queensland, the Northern Territory and Western Australia all sit out daylight saving inside countries that observe it. | 1 h | Convert to the specific city, not to the country. |
| Storing an offset instead of a zone | UTC-05:00 saved in a database is correct today and wrong after the next transition, because the offset has no rules attached to it. | 1 h | Store a UTC instant plus the IANA identifier, for example America/Toronto. |
| Scheduling in the transition hour | 02:00 to 03:00 local does not exist on the spring transition day and happens twice on the autumn one. | 1 h or undefined | Avoid that window entirely, or set the event in UTC. |
| Trusting a converter with no date field | A tool that only knows "now" cannot tell you about a meeting six weeks away that falls on the other side of a transition. | 1 h | Use a converter that asks for the date, and set it to the date of the event. |
The two errors at the top of the table account for most real-world failures. Both are solved by the same habit: never state a time without also stating where it is and when it is. For times written in the four-digit form used in aviation and healthcare, where a Zulu suffix marks UTC explicitly, see the Military Time Converter.
The full calendar date appears next to the time, not just a weekday name.
A city or a numeric offset appears, and no bare three-letter abbreviation does.
You have confirmed which participants are on a different calendar day.
The date is not a clock-change weekend, or if it is, the time is well away from 02:00.
The twelve terms that appear in every discussion of time zones, defined precisely.
+05:30 or -03:30. An offset describes a clock reading at a moment in time. It carries no information about future changes.Europe/Athens, not by an offset or an abbreviation.Z suffix on a timestamp. 1530Z means 15:30 UTC, and every reader converts to their own clock from there.For the calendar side of these problems, counting days between dates or shifting a date forward, use the Date Calculator. For arithmetic on durations rather than instants, the Time Calculator adds and subtracts hours, minutes and seconds directly, and the Time Duration Calculator measures the span between two moments.
Direct answers to the questions people ask most about this calculation.
Subtract three hours. Eastern Standard Time is UTC-05:00 and Pacific Standard Time is UTC-08:00, so 15:00 EST is 12:00 PST. The three-hour gap holds all year for cities that both observe daylight saving, such as New York and Los Angeles, because they switch on the same dates. It does not hold for Phoenix, which stays on UTC-07:00 through the summer and is therefore only two hours behind New York from March to November.
UTC is a time standard produced from atomic clocks and kept within 0.9 seconds of the Earth's rotation by leap seconds. GMT started as mean solar time at Greenwich and is now also the name of the winter time zone in Britain, Ireland and Portugal. They agree to within a second, but GMT as a zone becomes British Summer Time from late March to late October, while UTC never changes. Write deadlines in UTC.
Because the two places move their clocks on different dates. North America springs forward on the second Sunday in March while the European Union waits until the last Sunday in March, so for about three weeks the Toronto to London gap is four hours instead of five. In autumn the EU falls back a week before North America, producing a second four-hour window. Southern hemisphere zones move in the opposite direction entirely.
UTC+05:30 is India Standard Time, used across the whole of India, and also Sri Lanka. India runs a single zone across roughly 3,000 km of longitude and has not used daylight saving since 1945, so the offset is +05:30 every day of the year. Nepal, immediately to the north, sits fifteen minutes further ahead at UTC+05:45, which is one of only a handful of quarter-hour offsets in use.
No. Arizona stays on Mountain Standard Time, UTC-07:00, all year, so from March to November it matches Pacific Daylight Time in California rather than Mountain Daylight Time in Colorado. There is one exception inside the state: the Navajo Nation does observe daylight saving, which means part of northeastern Arizona is an hour ahead of the rest of it for eight months of the year.
It depends entirely on who wrote it. CST is Central Standard Time in the United States and Canada at UTC-06:00, China Standard Time at UTC+08:00, and Cuba Standard Time at UTC-05:00. The worst case is a fourteen-hour error, which also puts the meeting on a different calendar day. Never rely on the abbreviation alone: ask for a city name or a numeric offset, or convert everything to UTC.
Six: Pacific at UTC-08:00, Mountain at UTC-07:00, Central at UTC-06:00, Eastern at UTC-05:00, Atlantic at UTC-04:00 and Newfoundland at UTC-03:30. Newfoundland is the only Canadian zone on a half hour. Saskatchewan sits inside the Central zone but never changes its clocks, and Yukon moved to a permanent UTC-07:00 in 2020, so both stay put while their neighbours switch.
Late morning in London. In January, India is 5.5 hours ahead, so London 09:00 to 11:30 covers Mumbai 14:30 to 17:00, giving 2.5 shared hours. In July the gap narrows to 4.5 hours because London is on British Summer Time, which widens the overlap to about 3.5 hours from 09:00 to 12:30 London. Anything after midday London pushes the Indian side past 17:30.
Because standard time was adopted country by country, and several governments chose the offset closest to their own solar noon rather than the nearest whole hour. India is UTC+05:30, Nepal UTC+05:45, Iran UTC+03:30, Afghanistan UTC+04:30, Myanmar UTC+06:30, Newfoundland UTC-03:30 and the Chatham Islands UTC+12:45. Between them these zones cover well over a billion people, so they are not an obscure edge case.
No. Saskatchewan stays on UTC-06:00 all year. The practical result is that its clocks match Manitoba and the rest of Central Time in winter, then match Alberta and the rest of Mountain Daylight Time in summer, without anybody in the province touching a clock. Lloydminster is the exception: it straddles the Alberta border and follows Mountain Time with daylight saving on both sides of the city.
The calendar date jumps a full day. Travelling west across the line you skip forward a day, so a Friday departure from Toronto arrives in Tokyo on Saturday. Travelling east you repeat a day and can land before you took off by the clock. The elapsed flight time is unaffected: only the label on the moment changes. Work in UTC and the arithmetic stays simple.
It reads your browser's built-in copy of the IANA time zone database through the standard Intl date formatting interface. That database holds the daylight saving rules and offset history for every zone, and it ships with browser updates. Because the converter looks up the offset for the specific date you enter, a conversion for 15 July and the same conversion for 15 January give correctly different answers.
Zulu time is UTC, written with a Z suffix and spoken as the NATO alphabet letter for Z. A timestamp of 1530Z means 15:30 UTC exactly. It is standard in aviation, shipping and military communication precisely because it removes every zone ambiguity: everyone reads the same four digits and converts to their own clock. The same value is written 15:30 UTC or 15:30:00Z in civilian and ISO 8601 notation.
Anchor the invitation to the IANA zone of the person or office the meeting belongs to, for example Europe/Berlin, and let each attendee's calendar convert it. Never type a time into the invitation title without naming a zone. If the meeting is a hard deadline rather than a conversation, set it in UTC instead, because UTC never shifts and cannot be misread in any month of the year.