Thank you very much, Rob, for discussing our question and a detailed description your interesting application!
You are right, the native component of the clock and other components will save us from many difficulties and create workarounds.
As far as I understand, you use the Firebase component in your application and every user must log in to get the necessary information in real time. Then you can make a field on the basis of the unique user ID for the time stamp. Firebase works much faster than web-services (and timezonedb) and two calls instead of one should not be embarrassing.
“because otherwise all these devices are making calls to timezonedb or firebase”. No, the work of timezonedb and firebase differs in principle. Timezonedb really works on requests, which happens slowly, and firebase uses the event model and the update client data occurs when an event occurs, and not with persistent requests to the web server.
I do not know when a clock component can be implemented. Now I see in the documentation the announcement of the component Alert dialog.
Regards Alex