This guide covers Time Zone Converter Guide | TimeFlow — what it means, how it works, and how to use it. The explanations below are followed by worked examples with real dates and real times, a set of frequently asked questions, and links to the tools that do the calculation for you: the time zone converter, the world clock, and the UTC converter. Where a number is given — an offset, a date, a count — it is computed from the IANA Time Zone Database for the date stated, not copied from a table that may be out of date.

Try the tool: Time Zone Converter — convert any time between any two cities, with the daylight saving rules for the date you choose.

A time-zone converter takes a date and time in one place and tells you what time it is in another. It is the single most useful tool on this site, and the one people use when a meeting, a flight or a deadline depends on getting the time right.

Using it is straightforward: pick the date, pick the time, pick the two cities (or time zones), and read the answer. The converter on this site also shows the offset it used for each city on that date, so you can check the result. That matters, because the offset changes with daylight saving, and the answer depends on the date.

The most common use is scheduling. A meeting at 09:00 in New York is 14:00 in London in winter and 13:00 in London for three weeks in March, when the US has changed its clocks and Europe has not. A converter that knows the date gets this right; a converter that only knows the cities does not.

The other common use is travel. A flight that leaves New York at 18:00 and arrives in London at 06:00 the next day is a 7-hour flight, not a 12-hour one — the 5-hour time difference is in the arrival time. The flight time calculator on this site works this out, including the date change, which is the part people most often get wrong.

In practice

A time zone converter does one calculation: it takes a time in one city and gives the time in another. The calculation goes through UTC — convert the first city's time to UTC by subtracting its offset, then convert UTC to the second city's time by adding its offset. The time zone converter does it for any two cities, with the daylight saving rules applied for the date you choose.

The part that makes a converter useful is the date. The offset between two cities changes when one of them moves its clocks and the other does not — and the dates differ: the US changes three weeks before Europe in spring, and a week later in autumn. A converter that ignores the date will give the wrong answer for a few weeks a year. The good ones ask for the date, and apply the rules for that date.

The commonest use is the meeting invite. Before you send an invite, convert the proposed time into every participant's local time and check that it falls inside their working day — and that the date is the same for everyone, because a city 12 hours ahead is living in tomorrow. The meeting planner finds the times that suit everyone, and the world clock shows the current time in every city at a glance.

The numbers: what 12:00 UTC looks like around the world

The table below shows the local time in eight major cities when it is 12:00 UTC on 15 January 2026. The spread is the whole point of time zones: the same moment is a morning in New York, midday in London, evening in Mumbai and night in Tokyo.

City Local time when it is 12:00 UTC (15 January 2026) UTC offset
New York 7:00 am UTC−05:00
London 12:00 pm UTC+00:00
Paris 1:00 pm UTC+01:00
Dubai 4:00 pm UTC+04:00
Mumbai 5:30 pm UTC+05:30
Tokyo 9:00 pm UTC+09:00
Sydney 11:00 pm UTC+11:00
Los Angeles 4:00 am UTC−08:00

Two things stand out. First, the range: from 04:00 in Los Angeles to 23:00 in Sydney, the same instant covers almost the whole day. Second, the half hour: Mumbai is at 17:30, not 17:00 or 18:00, because India uses a half-hour offset (UTC+05:30). If you convert a time for Mumbai by rounding to the nearest hour, you will be half an hour out. The UTC converter shows the offset and the local time for any city on any date, and the time zone converter converts between any two cities directly.

The offsets change during the year for the cities that observe daylight saving. The same eight cities in January and in July:

City Offset in January 2026 Offset in July 2026 Changes?
New York UTC−05:00 UTC−04:00 Yes — one hour
London UTC+00:00 UTC+01:00 Yes — one hour
Paris UTC+01:00 UTC+02:00 Yes — one hour
Dubai UTC+04:00 UTC+04:00 No
Mumbai UTC+05:30 UTC+05:30 No
Tokyo UTC+09:00 UTC+09:00 No
Sydney UTC+11:00 UTC+10:00 Yes — one hour
Los Angeles UTC−08:00 UTC−07:00 Yes — one hour

New York, London, Paris, Sydney and Los Angeles all change by one hour between January and July; Dubai, Mumbai and Tokyo do not, because they do not observe daylight saving. That is why a conversion done in January can be wrong in July — and why the UTC converter asks for the date.

Key facts

  • UTC never observes daylight saving. It is the fixed reference that every other time zone is measured against.
  • The world uses 38 different UTC offsets, from UTC−12:00 to UTC+14:00 — a span of 26 hours.
  • Nepal is on UTC+05:45, the only 45-minute offset in regular use. India is on UTC+05:30.
  • The Prime Meridian is at 0 degrees longitude, through Greenwich, London.
  • A time written in UTC means the same thing everywhere on Earth, in January and in July.

Frequently asked questions

How does a time zone converter work?

It converts a time in one city to the time in another, going through UTC: subtract the first city's offset to get UTC, then add the second city's offset.

Why does a converter ask for the date?

Because the offset between two cities changes with daylight saving, and the dates differ by country. A converter that ignores the date gives the wrong answer for a few weeks a year.

What is the best time zone converter?

The time zone converter: pick any two cities and a date, and it gives the time in both, with the daylight saving rules applied.

Can I convert between more than two cities?

Yes — convert the time to UTC once, then add each city's offset. The world clock shows the same time in every major city at once.

How do I convert a meeting time for an invite?

Convert the proposed time into every participant's local time and check it falls inside their working day — and that the date is the same for everyone.

What time is it in Tokyo when it is 12:00 UTC?

23:00 the same day — Tokyo is UTC+09:00 all year, so you add nine hours to 12:00 UTC. In New York it is 07:00 in winter (UTC−05:00) and 08:00 in summer (UTC−04:00). The UTC converter shows the time in any city for 12:00 UTC.

What is the time difference between London and Tokyo?

Nine hours in January 2026: London is UTC+00:00 and Tokyo is UTC+09:00. In July it is eight hours, because London moves to UTC+01:00 while Tokyo stays on UTC+09:00. The time zone converter gives the difference for any two cities and any date.

Related pages

Sources

  • IANA Time Zone Database, via Node.js Intl (Intl.DateTimeFormat with timeZone) — offsets, daylight saving dates and local times in this article were worked out from the IANA database, not typed from memory.
  • TimeFlow's own time-zone data (data/cities.ts, data/dst.ts), computed from the IANA database.
  • Time zone rules and offsets: the IANA Time Zone Database, as applied by this site's tools. Offsets and daylight saving dates on this page are computed from the database for the dates stated.
  • TimeFlow's time zone converter, world clock and UTC converter — the live tools behind the numbers on this page.
  • Time-zone and daylight saving rules are set by governments and can change. For flights, deadlines and meetings that cannot move, confirm the time with an official source.