Scheduling across zones is mostly arithmetic, and the arithmetic is easy. What makes it hard is that the fair answer and the convenient answer are usually different people's mornings, and that an invitation written carelessly is read carelessly.
Write each person's working hours as a range in UTC and look for where the ranges overlap. Past about eight hours of separation there is usually no overlap at all, and the question becomes whose day to stretch rather than when everyone is free.
Between 13:00 and 16:00 UK time, which is morning on the US east coast and late afternoon in Europe. It is the widest genuine overlap: earlier excludes the US, later excludes continental Europe.
Early European morning, around 08:00 to 10:00 UK time, which is afternoon to early evening across South and East Asia. The window narrows the further east you go — with Tokyo it is effectively one hour.
There is no comfortable answer: the gap is 12½ to 13½ hours. The usual compromises are 08:00 Pacific, which is 20:30 in India, or 19:00 Pacific, which is 07:30 the next morning there.
Late afternoon Pacific time, which is the following morning in Sydney. A 16:00 Pacific meeting is 09:00 or 10:00 in Sydney the next day depending on daylight saving on both sides.
Take each city's working day, convert both to UTC, and measure the intersection. London and New York share about four hours; London and Singapore about one; San Francisco and Sydney none at all.
Rotate it. A standing call that is always early for the same office becomes a quiet tax on that office, and rotating it every other occurrence spreads the cost without extra negotiation.
Lead with one anchor time including its zone, then list the others: '15:00 London / 10:00 New York / 20:30 Delhi'. Send it as a calendar invitation with a zone attached so each recipient's software does the conversion too.
No — put it in the invitation's time field where software can read it. A zone typed into the title is invisible to every calendar and becomes wrong when daylight saving moves.
Strictly, 9am EST in July is 10am local time in New York, because New York is on EDT then. Most people writing 'EST' in July mean 9am local, which is why zone names beat abbreviations.
Far enough that nobody is deciding at 6am their time whether to attend — a few days for a small group, a week or more once three zones are involved. The constraint is not the calendar, it is that people in other zones cannot be asked at short notice.
It is rude to do it without asking, and normal to do it occasionally by agreement. The difference is whether the person had a chance to say no before the invitation arrived.
Treat lunch as a real block on the calendar rather than a convention. Scheduling tools that read availability only see what is written down, so an unmarked lunch is an hour that looks free.
Follow-the-sun means handing work between teams in different zones so something progresses around the clock. It needs handover notes rather than meetings, since the whole point is that the teams rarely overlap.
Three is manageable, four is uncomfortable, five means somebody is dialling in at midnight. Past three zones, consider recording it and taking comments asynchronously instead.
Yes, when zones make attendance genuinely awkward. A recording plus written notes turns a 6am obligation into a 20-minute catch-up and removes most of the pressure to find an impossible slot.
It is a policy that meetings stay inside everyone's declared working hours, and that anything outside them needs agreement. It works only if people's hours are actually published, because otherwise it's enforced by guesswork.
Check the calendars of every country involved before sending, not after. Holidays vary far more than working hours — a date that is ordinary in London can be a national holiday across India, the Gulf or East Asia.
That is the correct behaviour: everyone sees the same moment expressed in their own zone. A problem only exists if the underlying moment differs, which usually means the invitation was sent without a zone.
A time is one slot; a window is a range you are willing to meet in. Sending a window rather than a single slot across zones saves a round of email, because the other side can pick what suits them.
Send a booking link rather than proposing times. The other person picks from your real availability in their own zone, and neither of you does any arithmetic.
Convert them, and show your working. Writing both times costs you five seconds and removes the most common cause of somebody joining an hour late.
Tuesday to Thursday. Mondays lose to holidays and catch-up, and Friday afternoon in Europe is already the weekend in parts of the Middle East, where the working week runs Sunday to Thursday.
No. Across much of the Gulf and neighbouring countries — Saudi Arabia, Qatar, Kuwait, Bahrain, Oman, Egypt, Jordan and Israel among them — Friday and Saturday are the weekend, so a Friday meeting there is a weekend meeting. The UAE moved to a Saturday–Sunday weekend in 2022.
Shorter than a local one, and never a first-thing or last-thing 90 minutes. If somebody is joining at 7am or 9pm, respect for their hour matters more than covering the whole agenda.
Collect each person's zone and working hours once, then compute the intersection rather than asking every time. The answer changes only when somebody moves or the clocks do.
Then stop looking for one. Move the work to writing, and reserve live time for the rare decision that genuinely needs it — at a time you agree explicitly, each time.
The invitation, always. An email says the time once in one zone; an invitation puts it in every attendee's calendar in their own zone and updates if it moves.
Book buffers as real events rather than relying on discipline. A calendar that can see a five-minute gap will fill it, whoever's zone the next meeting is in.
Core hours are a window everyone agrees to be reachable, usually two to four hours wide, with the rest of the day left to each person. It is the smallest commitment that makes live conversation possible without pretending everyone works the same day.
Publish it rather than describe it. A booking page renders your real free time in the visitor's own zone, which is both more accurate than a list of slots and immune to going stale.
Because the US, Europe and Australia change clocks on different dates, so for a week or two the usual gap is an hour out. Nothing is broken; it corrects itself once both sides have changed.
Daykite is a calendar that holds meetings, routines, tasks and goals together, with an assistant that shows you every change before it makes it. Free for one person.