Agents and users in different timezones

I need to setup zammad to support users and agents in a range of timezones.
For this the server needs to default to UTC timezone (which is also missing from the global settings) and agents would need to be able to specify their timezone.

With most other software this is super easy as it has a global timezone setting and account specific overrides.

How can I implement this behaviour with zammad?

Zammad version 5.2.x

Forgive me if I’m mistaken, but I believe Zammad does have a global timezone setting already. Then all times displayed are in the Agents timezone. No need to set any account specific overrides.

I have the same thing. Agents across multiple timezones.

But there is no explicit profile value for the agents timezone if all user_preferences are enabled in the role.

How does the agents timezone gets determined?
Implicitly by the browser?