Time zone meeting planner

What time is it in — without doing the arithmetic

Subtracting time zones in your head fails more often than it should, and not because people are careless: it fails because the gap between two cities is not constant. London and New York sit five hours apart most of the year, but for three weeks in March they are four, because the United States moves its clocks before Europe does. Anyone who has scheduled a call during those weeks using “the usual difference” knows how that ends.

The grid removes the arithmetic entirely. Each row is a city, each column an hour of the day, and the colour tells you what is happening there at a glance: green if that person is inside their working hours, yellow at the edge of their day — just before they start or after they finish — and red if it is the middle of the night. Nothing to interpret: the greenest column wins.

Current local time in every city on the list

Under each participant you get their current time and their offset from UTC. That is useful even when you are not scheduling anything: add a city and you know whether it is a reasonable moment to message someone or whether you are about to wake their phone. Up to twelve cities, searchable by name — Bogotá, Tokyo, Sydney — or by zone identifier if you work with those and want to be precise.

The best time to meet across time zones, calculated rather than guessed

The best times button walks the day in half-hour steps and scores every one. The first rule is obvious: the slot where the most people are inside their working hours wins. The interesting rule is the second, which kicks in when no hour works for everyone — the normal case the moment Europe, the Americas and Asia are on the same call.

There it ranks by the worst sacrifice any single person has to make, not by the sum. That distinction matters: spreading two hours of inconvenience across two people beats loading four onto one, even when the total is identical. And not all bad hours are equal — staying online until 22:00 is annoying, getting up at 03:00 is another thing entirely, so deep night is penalised separately. That is why, for London, New York and Tokyo, it proposes the slot that puts Tokyo at 22:00 rather than the one that puts New York at 3 a.m.

Daylight saving, which is where nearly all of these tools break

Daylight saving rules are a minefield. Not every country observes it, the ones that do switch on different days, and in the southern hemisphere the direction is reversed. On top of that some zones dropped it recently, and others run offsets of half or three-quarters of an hour, like India and Nepal.

This tool does not maintain its own table of any of that: it uses the browser's own time zone database — the same one your operating system uses — which already carries those rules and updates itself. On top, for whichever date you choose, it checks whether any city on your list changes its clocks that week. If one does, it says so with the name, the day and both offsets, so you confirm the time with that person instead of discovering it on the day of the call.

A link everyone opens in their own time

The usual way to call an international meeting is to write “Tuesday at 15:00 CET” and hope. It works, sort of. Here you copy a link instead: it carries the whole meeting inside it — cities, hours and the chosen slot — and whoever opens it sees it with their own time zone added automatically, no sign-up, nothing to install. And if you would rather it lived in the calendar, the exported file imports into Google Calendar, Outlook or Apple Calendar; it is written in UTC, so everyone sees their own hour with no ambiguity.

The limits, stated before they bite

Up to twelve participants: more rows fit, but the grid stops being readable at a glance, which is the whole point of it. It plans one specific day, not a whole week. Best slots are computed in half-hour steps, not to the minute. And the daylight saving warning covers the window around your chosen date: if you schedule two months ahead and a change falls in between, the local times stay correct — the browser's database handles that — but the warning only appears when the change is near the date.

And if what you have in front of you is a log rather than a meeting — a bare number that needs turning into a date, and knowing which zone the server wrote it in — that is what the Unix timestamp converter is for, showing it at once in your zone, in UTC and in one you choose.