Working-hour overlap between major business cities
How much of the working day two cities actually share, how that changes through the year, and what to do when the answer is zero.
Before you look for "the best time to meet", it helps to know how much shared working time two cities actually have. The answer is often less than people assume, and it changes during the year as daylight saving starts and ends at different times in different places.
The table below shows the overlap of a standard 09:00–17:00 working day in both cities, on an ordinary Wednesday in January and in June 2027. The time-difference column shows every gap the pair goes through during the year, including the short "mismatch" weeks in spring and autumn. Everything here is computed from the IANA time zone database (2026c).
| City pair | Time difference (range over the year) | Northern winter Jan 2027 | Northern summer Jun 2027 |
|---|---|---|---|
| New York ↔ London | +4 h / +5 h | 3 h 09:00–12:00 New York = 14:00–17:00 London | 3 h 09:00–12:00 New York = 14:00–17:00 London |
| New York ↔ Berlin | +5 h / +6 h | 2 h 09:00–11:00 New York = 15:00–17:00 Berlin | 2 h 09:00–11:00 New York = 15:00–17:00 Berlin |
| Chicago ↔ London | +5 h / +6 h | 2 h 09:00–11:00 Chicago = 15:00–17:00 London | 2 h 09:00–11:00 Chicago = 15:00–17:00 London |
| San Francisco ↔ London | +7 h / +8 h | None | None |
| New York ↔ São Paulo | +1 h / +2 h | 6 h 09:00–15:00 New York = 11:00–17:00 São Paulo | 7 h 09:00–16:00 New York = 10:00–17:00 São Paulo |
| London ↔ Dubai | +3 h / +4 h | 4 h 09:00–13:00 London = 13:00–17:00 Dubai | 5 h 09:00–14:00 London = 12:00–17:00 Dubai |
| London ↔ Mumbai | +4.5 h / +5.5 h | 2.5 h 09:00–11:30 London = 14:30–17:00 Mumbai | 3.5 h 09:00–12:30 London = 13:30–17:00 Mumbai |
| Berlin ↔ Singapore | +6 h / +7 h | 1 h 09:00–10:00 Berlin = 16:00–17:00 Singapore | 2 h 09:00–11:00 Berlin = 15:00–17:00 Singapore |
| London ↔ Singapore | +7 h / +8 h | None | 1 h 09:00–10:00 London = 16:00–17:00 Singapore |
| Singapore ↔ Sydney | +2 h / +3 h | 5 h 09:00–14:00 Singapore = 12:00–17:00 Sydney | 6 h 09:00–15:00 Singapore = 11:00–17:00 Sydney |
| San Francisco ↔ Sydney | +17 h / +18 h / +19 h | 3 h 14:00–17:00 San Francisco = 09:00–12:00 Sydney | 1 h 16:00–17:00 San Francisco = 09:00–10:00 Sydney |
| San Francisco ↔ Tokyo | +16 h / +17 h | 1 h 16:00–17:00 San Francisco = 09:00–10:00 Tokyo | None |
| New York ↔ Mumbai | +9.5 h / +10.5 h | None | None |
| New York ↔ Tokyo | +13 h / +14 h | None | None |
| London ↔ Sydney | +9 h / +11 h | None | None |
"None" means there is no moment when both people are inside 09:00–17:00. It does not mean a meeting is impossible. It means someone has to start early or stay late, and you should decide who on purpose.
What the numbers tell you
Transatlantic: a short, reliable morning window
New York and London share three hours most of the year: 09:00 to 12:00 in New York, 14:00 to 17:00 in London. For two short periods (the last week of October and the second half of March) the gap shrinks to four hours and the overlap grows to four. Berlin and the rest of Central Europe lose another hour, leaving two. From the US West Coast there is no overlap with London for most of the year. Someone in San Francisco has to start at 08:00 or earlier to catch London before it leaves at 17:00.
Europe and India: the half-hour catch
India uses UTC+5:30 all year and has no daylight saving. London's gap to Mumbai is 4.5 hours in summer and 5.5 hours in winter, so a recurring 13:30 London call lands at 18:00 in Mumbai in summer but 19:00 in winter. Teams that set the call in summer often only notice in November.
US and Asia: there is no fair slot, only a rotated one
New York to Mumbai, New York to Tokyo and San Francisco to Mumbai have no overlap at all in a 09:00–17:00 day. The least-bad options are early morning in the US paired with evening in Asia, or late evening in the US paired with the next morning in Asia. For a recurring meeting, rotating between those two patterns is usually fairer than making the same people take the 21:00 call every week.
Hemisphere crossings move twice as much
London to Sydney moves between a 9-hour and an 11-hour gap, because Europe and Australia change their clocks in opposite directions. San Francisco to Sydney does the same between 17 and 19 hours. A slot that works in January can be two hours worse in June for one side.
Three time zones at once: a worked example
Adding a third city usually removes the overlap entirely. Here are the five UTC hours around midday for a New York, London and Mumbai team on 13 January 2027:
| Slot | New York | London | Mumbai |
|---|---|---|---|
| 11:00 UTC | 06:00 (early) | 11:00 (in hours) | 16:30 (in hours) |
| 12:00 UTC | 07:00 (early) | 12:00 (in hours) | 17:30 (late) |
| 13:00 UTC | 08:00 (early) | 13:00 (in hours) | 18:30 (late) |
| 14:00 UTC | 09:00 (in hours) | 14:00 (in hours) | 19:30 (late) |
| 15:00 UTC | 10:00 (in hours) | 15:00 (in hours) | 20:30 (late) |
No slot keeps all three inside 09:00–17:00. The realistic choice is 13:00 UTC: 08:00 in New York (an hour early), 13:00 in London (comfortable) and 18:30 in Mumbai (an hour and a half late). Splitting the pain this way is usually fairer than putting it all on one person. The meeting matcher scores every slot on exactly this basis, counting how many minutes each person spends outside their own working hours.
Practical rules for distributed teams
- Publish your team's overlap hours. If the shared window is 14:00–17:00 London time, protect it for meetings that need everyone and move status updates to written channels.
- Rotate the inconvenient slot. For pairs with no overlap, alternate between an early slot for one side and a late slot for the other.
- Re-check after every clock change. Use the daylight saving calendar to see when your pairs shift.
- Prefer Tuesday to Thursday. A Monday-morning slot in Sydney is still Sunday afternoon in California, and a Friday-afternoon US slot is already Saturday in Sydney and Tokyo.