code: public final void setUtc(final boolean utc) {
          if (dates == null || !Value.DATE_TIME.equals(dates.getType())) {
              throw new UnsupportedOperationException(
                      "TimeZone is not applicable to current value");
          }
          dates.setUtc(utc);
          getParameters().remove(getParameter(Parameter.TZID));
      }
docs: Resets the timezone associated with the property. If utc is true, any TZID parameters are removed and the Java
  timezone is updated to UTC time. If utc is false, TZID parameters are removed and the Java timezone is set to the
  default timezone (i.e. represents a "floating" local time)
  
  @param utc the UTC value