How to schedule a meeting across time zones without getting it wrong

The four-step method

1. Pick the date first. Time differences change through the year. The gap between London and New York is five hours for most of the year but four hours for two short periods each spring and autumn when one has changed its clocks and the other has not. The gap between Los Angeles and Sydney swings between 17 and 19 hours. Every conversion must be done for the actual date.
2. Anchor the meeting to UTC. Choose one instant, write it in UTC, and treat that as the truth. 14:00 UTC on March 12 is a fact; "2 PM Eastern" is an interpretation of it. If the invitation later gets forwarded to someone in a fourth zone, they can derive their time from the anchor without asking.
3. Name cities, not codes. Write "9 AM Chicago, 3 PM London, 8:30 PM Mumbai". Codes such as CST and IST are ambiguous and calendars parse them inconsistently.
4. Show the date for every participant. A 10 PM call in San Francisco is a 2 PM call tomorrow in Sydney. If the invitation does not say "tomorrow", somebody will join a day early.

Finding the overlap

With two zones, working-hours overlap is usually easy to see. With three or more it is a real constraint, and sometimes there is no slot that is inside 9 AM to 5 PM for everyone.

There is no hour in that table that is comfortable for all three. The honest answer is to rotate the inconvenience: hold this week's meeting at 15:00 UTC, which is early for San Francisco, and next week's at 08:00 UTC, which is late for San Francisco but fine for London and Mumbai. The meeting planner lays out up to six locations against one timeline and shades each one's working hours, so the least-bad slot is visible rather than calculated.

In January the same three cities sit at UTC-8, UTC+0 and UTC+5:30, so the whole table shifts: 15:00 UTC becomes 7 AM in San Francisco and 3 PM in London. That one-hour drift is the reason step one, picking the date, comes first.

Writing the invitation

A good invitation states the instant once and the local readings beside it. For example: "Project review, Thursday March 12, 14:00 UTC. That is 9:00 AM in Chicago, 2:00 PM in London, and 7:30 PM in Mumbai." Any reader can check their own reading against the UTC anchor, and a reader in Tokyo can derive 11 PM without asking.

Calendar applications do this conversion automatically when the event carries a proper zone identifier such as America/Chicago rather than a typed abbreviation. If you send a plain-text time, include the UTC anchor; if you send a calendar file, make sure the event is created in a named zone. The converter produces the local readings for as many clocks as you need from one shared instant.

Pitfalls worth a second look

• Changeover weeks. Europe changes clocks on the last Sunday of March and October; North America on the second Sunday of March and first Sunday of November. For two or three weeks each spring and autumn, transatlantic gaps are an hour off their usual value. The daylight saving guide lists the rules.
• Half-hour offsets. India, Iran, Newfoundland, central Australia and others sit on 30-minute offsets, and Nepal on 45. A mental "add nine and a half hours" is fine once; across a recurring series it is where errors creep in. The half-hour zones guide lists them.
• Places that do not change. Arizona, Hawaii, Queensland, most of Saskatchewan, and most of Asia and Africa keep one offset all year, so their gap with places that do change moves twice a year even though their own clock never does.
• Recurring meetings. A weekly 9 AM Chicago meeting drifts to 3 PM London for most of the year but 2 PM London for a fortnight each spring. Decide which city the series is anchored to and tell the others it will move.

See it on the site

• Meeting time finderUp to six locations on one timeline with working hours shaded, for the date you pick.
• Time zone converterOne instant, many clocks, each with its local date and a Today or Tomorrow marker.
• Conversion chartsHour-by-hour tables for common pairs, with a business-hours overlap note on each.