ZBXNEXT-250 asks for per-user timezone setting, this issue takes it a bit further.

it would be nice to have a way to configure multiple timezones in user profile.
then, in a non-obtrusive place, user could switch between the selected timezones (maybe part of a config dropdown widget in the upper right corner or so). if the default timezone is selected, there's no indicator about it. if a non-default one is selected, it is permanently shown in the upper right corner.
in the control, there is a link "configure timezones" that takes the user to that exact section of their profile.

such a feature would be very useful for international teams - quickly switching between timezones of different team members, utc and so on.