Scheduling across time zones

Pick one anchor zone and say what it is

Every proposed time needs a home. Decide which time zone the meeting is "really" in, usually the organiser's, and write it next to every time you put in front of people: "Tuesday 14:00 Nairobi" rather than "Tuesday 2 p.m." The moment a time appears without a zone, somebody will assume it is in theirs.

In FINDaTIME the poll itself carries the anchor zone. It defaults to the zone your browser reports, and you can change it when you create the poll. Voters open their link and see the slots in that zone first, with the zone named, and can switch the display to their own zone with one control. The conversion is done for them, which removes the most common mistake outright.

Find the overlap before you propose anything

Write down working hours for each location, in that location's local time, and convert each to the anchor zone. For Nairobi, London and New York on a normal autumn day, 09:00 to 18:00 local comes out as roughly 09:00 to 18:00, 11:00 to 20:00 and 16:00 to 01:00 in Nairobi time. The overlap is 16:00 to 18:00 Nairobi, which is a two-hour window and all the room you have.

That is why a poll should concentrate its slots in the overlap rather than scatter them across the day. Ten slots spread over a whole week look generous, but if eight of them fall outside the window for one location, that person will mark eight slots unavailable and the vote tells you nothing you did not already know. Three or four slots inside the overlap, on different days, usually works better.

When there is no overlap at all, for example Sydney, Nairobi and San Francisco, somebody is meeting outside working hours whatever you do. Say so openly, and use the rotation described below.

Watch the daylight saving boundaries

Clocks do not change on the same date everywhere. The United States and Canada move in mid-March and early November; most of Europe moves on the last Sunday of March and October; much of Africa, Asia and South America does not change at all. For two or three weeks each spring and autumn, the gap between London and New York is four hours instead of five, and a standing meeting that was 15:00 in one city quietly becomes 14:00 or 16:00 in the other.

If your proposed dates straddle one of those boundaries, propose the time in the anchor zone and let the tool convert for each date separately. A time zone picker that converts "Tuesday 14:00" once and applies the same offset to every week will get the week after the change wrong. FINDaTIME converts each slot by its own date, so a slot on 20 March and a slot on 3 April both show correctly for a voter in New York.

Share the inconvenient hours around

For a one-off meeting, the overlap decides it. For a recurring one, the overlap decides it the same way every week, and the same person is always the one eating dinner at the keyboard. Resentment builds slowly and then arrives all at once as a resignation from the group.

A simple rotation fixes it: alternate between two or three times, each comfortable for a different region. Run a fresh poll for each cycle with slots from each region's comfortable hours, and look at who marked what unavailable. The ranking in FINDaTIME puts slots nobody has ruled out ahead of everything else, so if a slot is genuinely impossible for one person you will see it, rather than discovering it when they do not turn up.

Write the invitation so it cannot be misread

Three habits save most of the confusion. Use the 24-hour clock, so 14:00 can never be read as 4:00. Name the city rather than an abbreviation, because "CST" is Central Standard Time in North America, China Standard Time and Cuba Standard Time, and "IST" is used in India, Ireland and Israel. And when the meeting is booked, send it as a calendar invitation rather than a line of text, because each person's calendar will show the event in their own local time without anyone converting anything. Booking a slot in FINDaTIME creates exactly that invitation, with the time zone embedded in the event.

A short checklist

• Choose an anchor zone and show it beside every time.
• Work out the overlap window first; put most of the slots inside it.
• Check whether a clock change falls inside your date range.
• For recurring meetings, rotate the time between regions.
• Use the 24-hour clock and city names, and finish with a calendar invitation.

Related: recurring meetings and standing groups. When you are ready, create a poll and let everyone see the times in their own zone.