This should be part of the "Whonix Workstation Control Panel". The user can change their time zone there, and the control panel does the background changes necessary to display that time zone in the current DE, but keep the system in UTC.

Is there a way to automatically get the timezone from the host or virtualizer?

No, it's better to leave it set to UTC. Not as long as we're not controlling the host (VBoxManage setextradata). Also this is better on a "if user wishes only" base.

That would be much better usability than asking the user to scroll through a list.

The most likely ones could be suggested after language selection that @troubadour is working on.

This should be part of the "Whonix Workstation Control Panel"

Or whonix-setup-wizard ?

Messing with config files might not be a robust solution.

Finding that out is the TODO of this ticket.

I don't think we should encourage users to set time zones because it can give away their geo location both for an adversary in the VM and for timestamp leaks by applications in the WS.

Good point.

What about hiding the clock in the task bar then by default?

I think hiding the clock is a bad idea as a user may want to manually run sdwdate to adjust it if it's out of whack before initiating internet traffic. (This is on non-Qubes versions lacking auto time adjust)