code: public final boolean inDaylightTime(final Date date) {
          final Observance observance = vTimeZone.getApplicableObservance(new DateTime(date));
          return (observance instanceof Daylight);
      }
docs: Determines if the specified date is in daylight time according to
  this timezone. This is done by finding the latest supporting
  observance for the specified date and identifying whether it is
  daylight time.
  
  @param date a date instance
  @return true if the specified date is in daylight time, otherwise false