This guide covers Business Hours Across Time Zones | 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a count — it is computed from the IANA Time Zone Database for the date stated, not copied from a table that may be out of date.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.

Business hours across time zones are the hours when two offices are both open. The standard working day is 09:00–17:00 local time, and when the offices are in different time zones, those windows may barely overlap — or not at all. New York (09:00–17:00) and London (09:00–17:00) overlap for three hours: 09:00–12:00 in New York is 14:00–17:00 in London. New York and Sydney barely overlap at all: when Sydney's working day ends at 17:00, it is 02:00 in New York.

The overlap is the most important number in international business, and it changes with daylight saving. New York and London are 5 hours apart in winter and 4 hours apart in summer, so their overlap grows from three hours to four in summer. New York and Sydney are 15 hours apart in the northern winter and 16 in the northern summer — and the overlap stays at zero either way, because the difference is so large that one city's working day is the other's night.

The practical answer is to find the overlap and protect it. The best meeting times between two cities are usually the hours that fall inside both working days, or at worst at the edge of one of them. A 09:00 call in New York is a 14:00 call in London and a 22:00 call in Tokyo — acceptable for London, late for Tokyo. A 16:00 call in New York is 21:00 in London and 06:00 the next day in Tokyo — bad for both.

For three or more cities, the overlap shrinks fast. New York, London and Tokyo have no hour that falls inside all three working days: the overlap of New York and London (14:00–17:00 London) is 23:00–02:00 in Tokyo. The usual solution is to rotate the pain — take turns holding the meeting at an awkward hour — or to accept that some participants will join outside working hours, and keep the meeting short.

In practice

The 9-to-5 working day is a local idea, and it does not travel. When it is 9am in New York, it is 2pm in London, 3pm in Paris, 6:30pm in Mumbai and 10pm in Tokyo. The overlap between New York and London is five hours; between New York and Tokyo it is almost nothing. The further apart the zones, the shorter the overlap, and the more the meeting has to be someone's early morning or late evening.

The practical fix is to rotate the pain. If a team spans New York, London and Tokyo, no single meeting time suits everyone — so the fair approach is to rotate the meeting time week by week, so the same people are not always the ones getting up early. The other fix is to stop meeting: write the update down, record the call, and let people watch it when they wake up. The best meeting across time zones is often no meeting at all.

Business hours also differ by culture. The working week is Monday to Friday in most of the world, but Sunday to Thursday in much of the Middle East, and Saturday is a working day in Israel. The working day starts at 9am in New York, 10am in much of Europe, and 8am in much of Asia. Knowing the local working hours matters as much as knowing the offset — a meeting at 9am New York time is 6:30pm in Mumbai, which is after the working day ends.

The numbers: working-hour overlap in January 2026

The table below shows the overlap of a normal 9am–5pm working day between four pairs of cities, in January 2026. The overlap is the window in which a meeting falls inside everyone's working day — and it shrinks fast as the distance grows.

Cities Overlap of working hours (9am–5pm local, January 2026) Best meeting time
New York and London 3 hours Mid-morning in New York, late morning in London
London and Tokyo None No overlap — someone meets outside working hours
New York and Tokyo None No overlap — someone meets outside working hours
London and Sydney None No overlap — someone meets outside working hours

The New York–Tokyo row is the one that matters most: there is no overlap at all, so any meeting between the two cities costs someone their evening or their early morning. The kindest time is 8am in Tokyo, which is 6pm the previous day in New York — or 6pm in New York, which is 8am the next day in Tokyo. The meeting planner shows the overlap for any set of cities, and the time zone converter converts any proposed time into every participant's local time.

The overlap changes in July, because the cities move their clocks in different directions. The same four pairs in July 2026:

Cities Overlap of working hours (9am–5pm local, July 2026)
New York and London 3 hours
London and Tokyo None
New York and Tokyo None
London and Sydney None

The London–Sydney overlap is the one that moves most: in January it is short, because Sydney is on daylight saving (UTC+11:00) and London is on standard time; in July it is longer, because Sydney is back on standard time (UTC+10:00) and London is on summer time (UTC+01:00). The gap shrinks from 11 hours to 9, and the overlap grows by two hours. A recurring meeting scheduled in January can be two hours better — or worse — in July, which is why the meeting planner is worth checking twice a year.

Key facts

  • The overlap between New York and London is five hours; between London and Tokyo it is two; between New York and Tokyo there is none.
  • A meeting time should always be written with its time zone — '3pm' on its own is meaningless across time zones.
  • Recurring meetings scheduled in local time can be an hour wrong after a clock change; scheduling in UTC avoids that.
  • The best meeting slot is usually mid-morning for the person furthest east and late morning for the person furthest west.
  • When there is no overlap, the fair approach is to rotate the time week by week so the cost is shared.

Frequently asked questions

What are business hours across time zones?

The hours that fall inside the working day in every city involved. For New York and London the overlap is five hours; for New York and Tokyo there is almost none.

What is the overlap between New York and London?

9am–12pm New York time, which is 2pm–5pm London time — five hours in which both cities are in their working day.

Is there an overlap between New York and Tokyo?

Almost none in a normal working day. Someone has to meet outside working hours — the kindest time is 8am in Tokyo, which is 6pm the previous day in New York.

Do all countries work Monday to Friday?

No. The working week is Sunday to Thursday in much of the Middle East, and Saturday is a working day in Israel. The working day also starts at different times — 9am in New York, 10am in much of Europe.

How do I find the overlap for my team?

Use the meeting planner: enter the cities and it shows the hours that suit everyone.

What is the overlap between London and Sydney in July?

About four hours in July 2026 — longer than in January, because Sydney is back on standard time (UTC+10:00) and London is on summer time (UTC+01:00), so the gap shrinks from 11 hours to 9. The meeting planner shows the overlap for any cities.

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.