Guide
Working hours overlap across time zones: how to find it, with a table for 20 city pairs
Overlap is the part of the day when two people are both at work. It decides when you can have a live call without someone getting up at dawn or staying up past midnight. Here's how to work it out, real numbers for 20 common city pairs, and what a job advert means by "must overlap 4 hours with EST".
How to find the overlap in three steps
- Write both working days in one city's time. If you work 9:00–17:00 in London and your client works 9:00–17:00 in New York, New York's day is 14:00–22:00 in London (in winter).
- Take the part that's in both. 14:00–17:00 London is inside both days: three shared hours.
- Check again after every clock change. Countries change their clocks on different dates, and many (Pakistan, India, the Philippines, the UAE, Singapore, Japan) never do, so the overlap moves during the year.
Shared 9-to-5 hours for 20 common city pairs
Times are for a normal 9:00–17:00 day in both cities, shown in the first city's time. January = northern winter, July = northern summer (dates for 2027).
| Cities | January | July |
|---|---|---|
| New York – London | 3 h (9:00–12:00 New York) | 3 h (9:00–12:00 New York) |
| Toronto – London | 3 h (9:00–12:00 Toronto) | 3 h (9:00–12:00 Toronto) |
| New York – Berlin | 2 h (9:00–11:00 New York) | 2 h (9:00–11:00 New York) |
| Los Angeles – London | None | None |
| New York – São Paulo | 6 h (9:00–15:00 New York) | 7 h (9:00–16:00 New York) |
| New York – Mexico City | 7 h (10:00–17:00 New York) | 6 h (11:00–17:00 New York) |
| London – Lagos | 7 h (9:00–16:00 London) | 8 h (the same hours) |
| London – Dubai | 4 h (9:00–13:00 London) | 5 h (9:00–14:00 London) |
| London – Karachi | 3 h (9:00–12:00 London) | 4 h (9:00–13:00 London) |
| London – Bangalore | 2½ h (9:00–11:30 London) | 3½ h (9:00–12:30 London) |
| London – Manila | None | 1 h (9:00–10:00 London) |
| London – Sydney | None | None |
| Berlin – Karachi | 4 h (9:00–13:00 Berlin) | 5 h (9:00–14:00 Berlin) |
| Berlin – Bangalore | 3½ h (9:00–12:30 Berlin) | 4½ h (9:00–13:30 Berlin) |
| Dubai – Karachi | 7 h (9:00–16:00 Dubai) | 7 h (9:00–16:00 Dubai) |
| New York – Karachi | None | None |
| New York – Bangalore | None | None |
| New York – Manila | None | None |
| Los Angeles – Sydney | 3 h (14:00–17:00 Los Angeles = 9:00–12:00 next day in Sydney) | 1 h (16:00–17:00 Los Angeles) |
| Singapore – Sydney | 5 h (9:00–14:00 Singapore) | 6 h (9:00–15:00 Singapore) |
For a few weeks in March, October and November the US and Europe are briefly out of step, and the US–Europe overlap grows by an hour. See the 2027 daylight-saving dates.
What "must overlap 4 hours with EST" means
Remote job adverts often ask for a few hours of overlap with US Eastern time, usually the client's morning (9:00–13:00 New York). This is what those four hours are on your clock:
| You work in | November to March | March to November |
|---|---|---|
| London | 14:00–18:00 | 14:00–18:00 |
| Berlin, Paris, Madrid | 15:00–19:00 | 15:00–19:00 |
| Kyiv, Cairo | 16:00–20:00 | 16:00–20:00 |
| Lagos | 15:00–19:00 | 14:00–18:00 |
| Nairobi | 17:00–21:00 | 16:00–20:00 |
| Karachi, Lahore | 19:00–23:00 | 18:00–22:00 |
| Bangalore, Mumbai | 19:30–23:30 | 18:30–22:30 |
| Ho Chi Minh City | 21:00–01:00 | 20:00–00:00 |
| Manila | 22:00–02:00 | 21:00–01:00 |
| Buenos Aires | 11:00–15:00 | 10:00–14:00 |
For US Pacific time (9:00–13:00 Los Angeles) add three hours: in Karachi that's 22:00–02:00 from November to March and 21:00–01:00 from March to November; in London it's 17:00–21:00 all year.
If you agree to an overlap like this, move your whole working day rather than adding the hours on top. A day of 14:00–22:00 in Karachi covers four hours of the New York morning in summer and still ends at a reasonable time.
How much overlap do you need?
- Client work: one or two reliable hours a day are usually enough for calls and quick questions.
- A team building something together: aim for three to four hours, so questions don't wait a full day for an answer.
- No overlap at all: work in writing, record short videos, and keep live calls for decisions.
When there's no overlap
- Stretch the edges. If one person starts at 8:00 and the other finishes at 18:00, many "no overlap" pairs get an hour.
- Rotate the late slot for recurring meetings, so the same person isn't always the one on the call at night.
- Hand over in writing at the end of each day: done, blocked, next.
See the overlap before you book. AlignHour suggests times that fit everyone's working hours, which you can set for each person, and warns you when a time is outside someone's day. Try any two cities in the free meeting planner.
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