Why the overlap is smaller than you think
A working day is eight hours wide. The planet is twenty-four hours around. That arithmetic is the whole problem, and it bites much sooner than people expect: two cities eight hours apart share exactly one hour, and one hour of shared time is not a working relationship, it is a standing appointment nobody can ever move.
Add a third city and the window does not shrink, it can vanish. Of the 14 common city pairs below, 8 have no moment at all that falls inside a 09:00–17:00 day at both ends in January — someone is always starting early or finishing late. That is the moment a team stops looking for a slot and starts deciding who is going to take the bad call, and how often.
The second thing people get wrong is treating the gap as fixed. It is not. Daylight saving does not start on the same date in every country, several countries do not observe it at all, and the southern hemisphere runs in the opposite direction. Between two cities the difference can be five hours for ten months and four for two weeks. The table below shows both, in January and in July, so you can see which of your pairs actually move.
Common city pairs, in January and July
Overlap of a 09:00–17:00 working day, calculated for 15 January and 15 July 2026. Where no such overlap exists, the closest workable window is shown instead and flagged outside hours — that means it lands within two hours before or three hours after someone's day, not inside it. A day boundary crossed is marked +1d.
| Pair | Overlap in January | Hours | Overlap in July | Hours |
|---|---|---|---|---|
| New York ↔ London | 09:00–12:00 New York 14:00–17:00 London |
3h | 09:00–12:00 New York 14:00–17:00 London |
3h |
| Los Angeles ↔ London | 07:00–12:00 Los Angeles 15:00–20:00 London outside hours |
5h | 07:00–12:00 Los Angeles 15:00–20:00 London outside hours |
5h |
| New York ↔ Los Angeles | 12:00–17:00 New York 09:00–14:00 Los Angeles |
5h | 12:00–17:00 New York 09:00–14:00 Los Angeles |
5h |
| London ↔ Bangalore | 09:00–11:30 London 14:30–17:00 Bangalore |
2.5h | 09:00–12:30 London 13:30–17:00 Bangalore |
3.5h |
| New York ↔ Bangalore | 07:00–09:30 New York 17:30–20:00 Bangalore outside hours |
2.5h | 07:00–10:30 New York 16:30–20:00 Bangalore outside hours |
3.5h |
| Berlin ↔ Bangalore | 09:00–12:30 Berlin 13:30–17:00 Bangalore |
3.5h | 09:00–13:30 Berlin 12:30–17:00 Bangalore |
4.5h |
| London ↔ Singapore | 07:00–12:00 London 15:00–20:00 Singapore outside hours |
5h | 09:00–10:00 London 16:00–17:00 Singapore |
1h |
| London ↔ Tokyo | 07:00–11:00 London 16:00–20:00 Tokyo outside hours |
4h | 07:00–12:00 London 15:00–20:00 Tokyo outside hours |
5h |
| Los Angeles ↔ Singapore | 15:00–20:00 Los Angeles 07:00–12:00 Singapore +1d outside hours |
5h | 16:00–20:00 Los Angeles 07:00–11:00 Singapore +1d outside hours |
4h |
| London ↔ Sydney | 07:00–09:00 London 18:00–20:00 Sydney outside hours |
2h | 07:00–11:00 London 16:00–20:00 Sydney outside hours |
4h |
| New York ↔ Sydney | 15:00–20:00 New York 07:00–12:00 Sydney +1d outside hours |
5h | 17:00–20:00 New York 07:00–10:00 Sydney +1d outside hours |
3h |
| Berlin ↔ São Paulo | 13:00–17:00 Berlin 09:00–13:00 São Paulo |
4h | 14:00–17:00 Berlin 09:00–12:00 São Paulo |
3h |
| Madrid ↔ Mexico City | 16:00–17:00 Madrid 09:00–10:00 Mexico City |
1h | 15:00–20:00 Madrid 07:00–12:00 Mexico City outside hours |
5h |
| Los Angeles ↔ Bangalore | 17:30–20:00 Los Angeles 07:00–09:30 Bangalore +1d outside hours |
2.5h | 18:30–20:00 Los Angeles 07:00–08:30 Bangalore +1d outside hours |
1.5h |
Calculated from the IANA time zone database as shipped with this page's build. For any other combination, or for a date where the rules have since changed, use the planner above — it reads the database in your own browser, which your operating system keeps current.
What to do when there is no overlap
- Move the boundary, not the meeting. Shifting one person's day by an hour is a smaller ask than it sounds, and it frequently opens a window that did not exist. Try 08:00–16:00 in the eastern city before concluding it cannot be done.
- Rotate the pain. If someone has to take a call outside their hours, the question is not who but how often. A fixed 22:00 call for the same person every week is a resignation letter with a six-month fuse.
- Stop meeting. A team spread across twelve hours is telling you something: the work needs to survive without synchronous contact. That is a documentation and handover problem, not a scheduling one.
- Check the date, not the month. If the meeting is recurring and it lands near late March or late October, it will move relative to at least one participant. Put the recurrence in a calendar that stores time zones rather than fixed clock times.
Frequently asked questions
Why do three time zones so often have no overlap at all?
Because a 9-to-5 day is only eight hours wide and the planet is twenty-four hours around. Two cities up to eight hours apart will always share something; add a third far enough away and the shared window can close completely. San Francisco, London and Singapore is the classic example — there is no hour of the day that falls inside 09:00–17:00 in all three, which is why teams spread that wide end up rotating who takes the awkward call rather than looking for a slot that does not exist.
Why does the answer change between summer and winter?
Daylight saving. Not every country observes it, those that do not switch on the same date, and the southern hemisphere runs opposite to the northern one. For a few weeks in March and again in late October or November, the gap between two cities is an hour different from what it is the rest of the year. London and New York are five hours apart for most of the year but four for two weeks in March, because the US changes clocks before the UK does.
Does this planner know about daylight saving in each country?
It does not need its own table. The calculation runs on your browser’s time zone database, which your operating system keeps updated, so the answer reflects the rules actually in force on the date you pick, including changes announced since this page was written.
What is a reasonable working window to assume?
The planner defaults to 09:00–17:00 and marks two hours before and three hours after as workable but unsociable, which is roughly where most people draw the line between inconvenient and unacceptable. If your team genuinely starts at eight or finishes at six, change the hours — a one-hour adjustment often turns a dead calendar into a real slot.
Counting the other cost of a distributed team? The team software cost calculator works out what your tool stack actually bills at your headcount.
How this works
There is no server and no time zone table of our own. Every conversion runs in your browser against the IANA database it already ships with, through the standard Intl date API, which is why the answer accounts for daylight saving on the specific date you choose rather than applying a fixed offset. Nothing you enter is sent anywhere.
The day is scanned in thirty-minute steps. A slot counts as working when it falls inside everyone's chosen hours, unsociable when it falls up to two hours before or three hours after them, and outside beyond that. Those margins are a judgement, not a standard — adjust the working hours if yours differ.