code: public GlobalizationPreferences setTimeZone(TimeZone timezone) {
          if (isFrozen()) {
              throw new UnsupportedOperationException("Attempt to modify immutable object");
          }
          this.timezone = (TimeZone) timezone.clone(); // clone for safety;
          return this;
      }
docs: Sets the timezone ID.  If this has not been set, uses default for territory.
  
  @param timezone a valid TZID (see UTS#35).
  @return this, for chaining
  @hide draft / provisional / internal are hidden on Android