By time zone, I assume you mean the definition for a specific geographical locale. The definition of that "time zone" definition is outside our control. Time zone definitions are the domain of the locale governing authority. The registration in the IANA db would have to be open too, for other practical reasons (e.g., how can a registrar check the authorization of a submission?).
May be we should discuss the registration process and the change control process? I have been assuming that it would be the same as is used for the MIME multimedia content type registrations.