Set timezone globally

[ela-kotulska-frequenz]

What's needed?

Timezone is hardcoded now in many places in the code. We use: datetime.now(tz=pytz.UTC) everywhere.

Proposed solution

We should set timezone once globally at the start of the program.
https://stackoverflow.com/questions/1301493/setting-timezone-in-python

Use cases

Otherwise module that forgot timezone would work wrong.

Alternatives and workarounds

Have one global config variable for the timezone.

Additional context

No response

[leandro-lucarella-frequenz]

We should always use datetime objects that are timezone aware, so this is not needed if we do that.