ZoneInfo is an app for iOS, iPadOS, and macOS to view the time zones in the system’s time zone database.
The app reads from
/usr/share/zoneinfo/zone.tab which is discussed in https://data.iana.org/time-zones/tz-link.html
Each entry in the file contains the identifier for a time zone and the coordinate of the exemplar location for that time zone.
ZoneInfo places each entry on a map as a pin- selecting a pin shows details about the time zone. Each pin is colored by its offset from GMT so that the user may visualize regions that observe the same local time.