How to use multiple time zones in Apple Calendar

Out of the box, Apple's Calendar shows everything in your Mac's current time zone and never mentions the subject again. That is fine until you book a call with someone abroad, or travel, and discover an event has quietly moved. The setting that fixes it is switched off by default and is not where most people look.

How do I turn on time zone support in Apple Calendar?

Four steps, using Apple's own wording:

1. Open the Calendar app.
2. Choose Calendar > Settings, then click Advanced.
3. Select "Turn on time zone support".
4. Click the pop-up menu to the left of the Calendar search field and choose the time zone you want.

Once it is on, Apple notes that "a time zone menu appears to the left of the search field". That menu is now the lens you are viewing your whole calendar through.

What actually changes when it is on?

By default, as Apple puts it, "calendar events are displayed in your computer's current time zone". With time zone support enabled you can change that view, and you can set individual events to use a different zone from the rest.

There is one behaviour worth understanding before you start flipping the menu, because it surprises people. Apple's guidance is explicit: "If you change your calendar's time zone, new events use the new time zone. When you switch back to the time zone that your Mac is using, events created in the other time zone keep that time zone."

In other words the setting is sticky per event. An event you created while viewing Tokyo stays a Tokyo event. That is usually what you want, but it does mean a stray change to the menu can leave you with a handful of events anchored to a zone you were only briefly looking at.

How do I set a time zone for one event?

With time zone support switched on:

1. Double-click the event, or force click it.
2. Click the event's date to open the detail popover.
3. Use the Time Zone pop-up menu.

You can pick a specific zone, choose Other for anything not in the list, or choose Floating. Floating is the interesting one: Apple describes it as keeping "the event from moving when you view a different time zone". A daily 8am gym slot should float, because you want it at 8am wherever you are. A call with a client in Chicago should not float, because that call happens at a fixed moment regardless of where you happen to be sitting.

The limitation: one zone at a time

This is where Apple Calendar stops, and it is worth being clear about it because the setting sounds more powerful than it is. Time zone support lets you view your calendar through one zone at a time and tag events with a zone. It does not give you a side-by-side view of several zones, and it will not tell you which hours your colleagues in three countries have in common.

So if your question is "what time is this event in Sydney?", Apple Calendar answers it: switch the menu to Sydney. If your question is "when can these six people all meet?", it cannot help, and neither can Google Calendar, which has a similar display-only ceiling.

What to use when you outgrow it

The point at which the built-in setting stops being enough is usually the point at which you are scheduling for other people rather than reading your own diary. That is a different job, and it wants a different tool.

Atlas sits in the menu bar and does exactly that part: your people on a world map with their working hours shaded, the fairest overlapping slot suggested automatically, and the event written to your calendar in everyone's correct local time in one tap. It writes to Apple Calendar, so the setting above still applies to the result. It is $4.99 once, with no account.