How to use display-time-world to show time in specific time zones?

[N. Jackson]

I'm wondering how to use display-time-world to display the time in
specific time zones.

The doc string for zoneinfo-style-world-list, which IIUC is the list of
time zones used by display-time-world says:

    zoneinfo-style-world-list is a variable defined in ‘time.el’.
    Its value is (("America/Los_Angeles" "Seattle")
     ("America/New_York" "New York")
     ("Europe/London" "London")
     ("Europe/Paris" "Paris")
     ("Asia/Calcutta" "Bangalore")
     ("Asia/Tokyo" "Tokyo"))

    Documentation:
    Alist of zoneinfo-style time zones and places for ‘display-time-world’.
    Each element has the form (TIMEZONE LABEL).
    TIMEZONE should be a string of the form AREA/LOCATION, where AREA is
    the name of a region -- a continent or ocean, and LOCATION is the name
    of a specific location, e.g., a city, within that region.
    LABEL is a string to display as the label of that TIMEZONE’s time.

But these values are _places_ not time zones. I'm wondering how, for
example, one would add UTC to the list?