code: public void setDefaultTimezone(TimezoneAssignment timezone) {
  		if (timezone == null) {
  			if (defaultTimezone != null && !propertyTimezones.values().contains(defaultTimezone)) {
  				assignments.remove(defaultTimezone);
  			}
  		} else {
  			assignments.add(timezone);
  		}
  
  		defaultTimezone = timezone;
  	}
docs: <p>
  Sets the timezone to format all date/time values in (by default, all
  dates are formatted in UTC).
  </p>
  <p>
  The default timezone is not used for properties that are configured to
  use their own timezone (see {@link #setTimezone}).
  </p>
  @param timezone the timezone or null to use UTC