I've built an app in Swift to view local time of my friends in the menubar with their photo and name, not just city names. But it also supports adding abbrs (such as PST, GMT, CEST), cities, and UTC offsets.All the data is stored locally via GRDB.swift. It uses MapKit to search in cities and find the timezones. The UI is built in Swift UI.
Website: https://there.pm
Happy to answer more questions