Comment by dcrazy

In the macOS version of Calendar, “Time Zone Support” is the name of a feature in the Settings window. When you check that checkbox, twi things happen: - the event inspector adds a timezone selector the the Start and End date/time pickers - the window titlebar gains a timezone picker.

The timezone picker in the window titlebar defaults to your system’s current timezone. When you create an event, the start and end times for that event default to the window’s current timezone.

You can use the newly-revealed picker in the inspector to change the timezone of an event. There is a single picker that alters both the start and end time. If you set this to something other than the timezone chosen in the window’s titlebar, the event will move to reflect when it will occur in the window’s timezone.

I am personally convinced this is what people want 99% of the time, and I think it’s silly that you have to check a checkbox in Calendar Settings to get it. It’s fairly common to receive details for an event in another timezone, such as a conference call or vacation. I live with Time Zone Support enabled on all my Macs, and while I rarely touch the timezone picker in the titlebar I make frequent use of the timezone picker when setting the event details window.

There’s one special option in the event details timezone picker: “Floating”. This tells Calendar to always reckon the start and end times in the timezone selected in the window’s titlebar. So if you create an event that starts at 7am and set its timezone to “Floating”, the event will always be shown to begin at 7am even if you change your system’s timezone or the timezone in the titlebar. I don’t use this feature much, but it’s useful for plotting out your daily routine. If you go for at 6am every day, regardless of where you are on the planet, you can create a floating “Daily Run” event that starts at 6am and doesn’t shift as you travel.

The iPhone version of calendar is designed differently. There is no “Time Zone Support” checkbox on iPhone. The event details view always shows time zone pickers for both the start and end times. This lets you create an event with the start and end times specified in local times in different timezones. I use this feature for every single flight I take, and I always have to enter them on my phone because the Mac doesn’t let you set the start and end timezones independently.

But the iPhone doesn’t let you choose Floating in the time zone picker, so you can’t use it to create daily-routine events. Thankfully, all versions of Calendar preserve the data and behavior of events created on any platform, so you can create your Floating events in a Mac and your timezone-spanning flights on an iPhone and they will render as expected on the other device, including the Event Details window.