World Time Zone Converter

What this converter does

Pick a reference city, type a date and time as it appears on a wall clock in that city, and press Convert. The same instant is then shown as local time in all eleven listed cities, together with each city's offset from UTC, a note when the local date differs from the reference date, and a marker when daylight saving time (DST) is in effect. It is built for the everyday jobs: scheduling a call across continents, checking when a livestream starts, or working out whether it is too late to phone a colleague. Leave the time field empty and the page uses the current moment of your device clock, read as the reference city's time.

One point catches many people out: the value you type is the reference city's wall-clock time, not your computer's time. If you live in London and want to know what 9:00 a.m. in New York means elsewhere, set the reference city to New York and enter 09:00.

How the arithmetic works

Every civil time is Coordinated Universal Time (UTC) plus an offset. Converting between two cities is always the same three steps:

1. Subtract the reference city's offset from its local time to get UTC. (Tokyo 09:00 with an offset of +9 hours is 00:00 UTC.)
2. Add the destination's offset to that UTC time. (00:00 UTC plus an offset of -5 hours is 19:00 on the previous day.)
3. If the result crosses midnight, move the date forward or back as well.

The catch is that a city's offset is not constant through the year. This page does not store a fixed table of offsets. It asks the browser, through the standard Intl.DateTimeFormat API, how a given city formats the exact instant being converted, and derives the offset from the difference. So the result follows whatever rules the browser's copy of the IANA time zone database holds for that date.

IANA zone names and why they beat abbreviations

Each city in the menu is stored as an IANA time zone identifier in the form Area/Location, such as America/New_York, Europe/London or Asia/Kolkata. An identifier names a place together with its full history of rule changes, which is different from an abbreviation. Abbreviations such as CST or IST are ambiguous: CST can mean Central Standard Time in North America or China Standard Time, and IST can mean India, Ireland or Israel. When you share a meeting time, a city name or a UTC offset on the specific date avoids misunderstandings that an abbreviation invites. Note also that a country can span several zones, so "New York" is representative of the US Eastern zone, not of the whole United States.

UTC offsets by city (reference table)

The table is computed when this page is built, using the same time zone database approach as the tool. It samples two dates, 15 January 2026 and 15 July 2026, one in each half of the year, and compares each city with New York. Daylight saving rules are set by governments and can change, so treat the table as an illustration and confirm important schedules against an official source or current time zone data.

The difference columns show the city's clock minus New York's clock, in hours. A value of -14 means that when it is noon in New York, it is 22:00 on the previous day in that city. A "Yes" in the last column means the offset on 15 January differs from the offset on 15 July, which is what a city with daylight saving looks like. Sydney is in the southern hemisphere, so its clocks run ahead in the northern winter. New Delhi's offset of +5:30 shows that not every offset is a whole number of hours.

Worked examples (checked with the same Intl calculation)

Example 1. Tokyo, Thursday 15 January 2026, 09:00 is 00:00 UTC. At that instant London is at 00:00 on the same Thursday, Sydney shows 11:00 on Thursday, and New York is at 19:00 on Wednesday 14 January. The date differs in New York, which the tool flags as "previous day".

Example 2. London, Wednesday 15 July 2026, 12:00 is 11:00 UTC, because London is on summer time (UTC+1) in July. Then Tokyo reads 20:00, New Delhi 16:30, New York 07:00 and Los Angeles 04:00, all on the same Wednesday. A 07:00 start is an early call for New York, which is the kind of thing worth noticing before sending an invite.

Example 3. Los Angeles, Thursday 15 January 2026, 20:00 is 04:00 UTC on Friday. Tokyo then shows Friday 13:00 and New Delhi Friday 09:30, so an evening in California is already tomorrow afternoon in Japan.

Mistakes and limits to know about

• Transition weeks. Different regions change their clocks on different dates, so for a few weeks a year the gap between two cities is an hour different from normal. A recurring meeting fixed at one hour in one city can drift by an hour for the other participants. Check the dates around the changeovers.
• Hours that do not exist, and hours that happen twice. When clocks spring forward, one local hour is skipped; when they fall back, one hour occurs twice. If you enter a skipped time, this tool adjusts it to a valid time and shows a notice. For an hour that occurs twice, a local time alone does not identify one instant, and the page picks a single interpretation without warning. Avoid scheduling in those hours, or state the UTC time.
• City is not country. The eleven cities are examples of their zones. Other places in the same country may use a different offset.
• Data comes from your browser. The tool relies on the time zone data bundled with your browser, which is updated with the browser itself. Very old or far-future dates can be affected by rule changes that your browser's data has not yet incorporated.
• Whether a zone uses DST. The "DST" marker is inferred by comparing the offset on the date with the offsets of January and July of that year. Some regions have changed or abandoned daylight saving in the past, so verify unusual cases.
• Not for legal deadlines. For flights, contracts or filing deadlines, rely on the official wording and the time zone it names.

Putting the result to use

1. For a group meeting, convert once, then scan the list for anyone whose local time falls outside reasonable working hours. Shift the reference time an hour at a time until the worst case is acceptable.
2. Use Copy results to paste the full list into a chat or an invite. Each line includes the date, weekday and offset, so recipients do not have to do their own arithmetic, and lines for a different date are marked.
3. For one-off events such as a livestream or a deadline, enter the exact date so the offsets for that day are used. For recurring events, re-check around each region's changeover.

Frequently Asked Questions

Related tools

• World Time Zone Converter (city-to-city)
• D-Day Countdown Calculator
• Currency Converter