The one rule
A good meeting time is one where nobody is asleep and nobody is eating dinner with their family. That gives each person a window of roughly 8 AM to 6 PM local, with the edges at 7 AM and 7 PM if someone is willing to stretch. Everything below comes from overlapping those windows. Check any specific date on the meeting planner, because daylight saving moves the overlaps by an hour twice a year.
The cheat sheet
Times are given in the first city's clock. "Good" means both sides are inside normal working hours. "Stretch" means one side is early or late but awake.
| Between | Good window | Stretch | Note |
|---|---|---|---|
| New York and London | 9 AM to 12 PM NY | 8 AM NY | The easy one. Five hours apart most of the year, four for two weeks in March. |
| New York and Paris / Berlin | 9 AM to 11 AM NY | 8 AM NY | Six hours apart. Noon NY is 6 PM in Paris, already late. |
| San Francisco and London | 8 AM to 9 AM SF | 7 AM SF | Eight hours. Only the first hour of the SF day works. |
| New York and Mumbai / Bangalore | 8 AM to 9 AM NY | 7 AM NY, or 7 PM NY | 9½ hours. 8 AM NY is 5:30 PM in India. Evening NY is Indian morning. |
| London and Mumbai | 9 AM to 12 PM London | 1 PM London | 4½ hours. Comfortable. |
| London and Singapore / Hong Kong | 9 AM to 10 AM London | 8 AM London | Seven or eight hours. Morning London, late afternoon Asia. |
| New York and Tokyo | None | 7 PM NY, or 7 AM NY | 13 hours. Someone is always outside working hours. Evening NY is Tokyo morning. |
| New York and Sydney | None | 6 PM NY, or 7 AM NY | 14 to 16 hours depending on the season. Same problem as Tokyo. |
| London and Sydney | 8 AM to 9 AM London | 7 AM London | 9 to 11 hours. Early London, late Sydney afternoon. |
| San Francisco and Singapore | None | 5 PM SF, or 6 AM SF | 15 hours. The famous impossible pair. |
The pairs with no good hour
Three of the rows above say "none," and they aren't mistakes. New York and Tokyo are 13 hours apart, which means one side's 9 AM is the other side's 10 PM. There is no hour where both are at their desks. The same goes for New York and Sydney, and for San Francisco and Singapore. Add a third city, like London, and it gets worse: San Francisco, London and Singapore together have no hour where even two of the three are comfortable and the third is merely stretching.
Teams that live with this do one of three things. They rotate the pain, so the late-night slot moves from one office to the next each week. They split the meeting into two shorter ones that each cover part of the group, with notes shared between them. Or they stop meeting live for routine updates and use written updates instead, saving the painful hour for things that really need everyone's voice.
Small things that prevent big mistakes
Write the time zone next to every time, every time. "3 PM" alone causes more missed calls than any calculation ever did. Name the city rather than the abbreviation: "3 PM Chicago" is clear, "3 PM CST" gets confused with China Standard Time. Check the date, not just the time, for anything crossing the Pacific, because the meeting may be tomorrow for them. And remember daylight saving: a recurring call pinned to New York time shifts by an hour for Sydney twice a year, in opposite directions, so the slot that worked in May breaks in October.
Test any combination on the meeting planner, which colors every hour green, amber or red for up to five cities. For a single moment, the converter shows what 10 AM in one city is everywhere else, and the UTC converter is the cleanest way to share a time with a scattered team.