code: public TimezoneAssignment getTimezoneToWriteIn(ICalProperty property) {
  		TimezoneAssignment assignment = getTimezone(property);
  		return (assignment == null) ? defaultTimezone : assignment;
  	}
docs: <p>
  Determines the timezone that a particular property should be formatted in
  when written to an output stream.
  </p>
  <p>
  Note: You should call {@link #isFloating} first, to determine if the
  property's value is floating (without a timezone).
  </p>
  @param property the property
  @return the timezone or null for UTC