In Windows 11, the built-in way to show other time zones with the taskbar clock is to add additional clocks.
- Open Control Panel.
- Set View by to Large icons.
- Select Date and Time.
- Open the Additional Clocks tab.
- Check Show this clock for each extra clock to add.
- Select the required time zone and enter a display name.
- Select OK.
After saving, clicking or hovering over the date/time area on the taskbar shows the extra clocks along with the local time.
If only comparing times is needed, the Clock app also supports this:
- Open Start and launch Clock.
- Select World clock.
- Select Add a new city.
- Add the required locations.
- Use Compare to compare times.