Finding a meeting time across Seoul, Tokyo, London and New York
Why some city pairs have no shared working hours, how daylight saving moves the overlap twice a year, and a quick way to check.
Scheduling a call between Asia and Europe or the US is mostly arithmetic, but a few details make it easy to get wrong. Here are the patterns worth knowing before you send an invite.
Some pairs barely overlap
With everyone working 9:00–18:00 local time:
- Seoul or Tokyo and London: in summer (British Summer Time) the overlap is a single hour, 17:00–18:00 in Seoul and Tokyo, 9:00–10:00 in London. In winter it disappears: London is one hour further behind.
- Seoul or Tokyo and New York: there is no overlap at all. When it is 9:00 in New York, it is 22:00 or 23:00 in Seoul.
- Seoul and Tokyo: the same clock all year, as neither observes daylight saving.
For pairs with no overlap, someone has to meet outside their working day. Rotating who takes the early or late slot is fairer than always asking the same side.
Daylight saving moves the overlap
Korea and Japan do not change their clocks, but Europe and North America do, and not on the same dates. Seoul is eight hours ahead of London in summer and nine in winter. For a few weeks each spring and autumn, London and New York are four hours apart instead of five. A recurring meeting that worked in September can land an hour earlier or later in November.
The safest habit: when a meeting recurs across a change date, check the first occurrence after the change.
Half-hour time zones
India is UTC+5:30, and a few other places also sit on half-hour or 45-minute offsets. A 9:00 start in Mumbai is 12:30 in Seoul, so an hour-by-hour grid can look slightly off. Allow for the extra half hour.
Check it quickly
The time zone converter & meeting planner puts two or three cities on a 24-hour strip, with each city’s working hours (9:00–18:00 by default, night shifts allowed) and the hours when everyone is working highlighted. Offsets come from your browser’s own time zone data, so daylight saving is applied for the date you choose.
If the problem is matching real calendars rather than time zones, that is what WhenWeave is for: it finds the time two people are both free, and the other person sees only that you are busy, not what you are doing.