Simultaneous time zones
Tap on the globe icon at the bottom left of the single day view, just above the list, to see time zones. Add the ones you want. Rotate the dial to move all times at once, superimposed on your schedule. You can name a time zone whatever you like, and even use emojis if you prefer.
Time zone tracking
Once you’ve added a time zone, a tiny dot will appear on the edge of your main day view, in the color you’ve chosen for it. This lets you ambiently keep an eye on what time it is in the places that matter to you.