code: public final boolean add(final Period period) {
          if (isUtc()) {
              period.setUtc(true);
          }
          else {
              period.setTimeZone(timezone);
          }
          return periods.add(period);
      }
docs: Add a period to the list.
  
  @param period
  the period to add
  @return true
  @see java.util.List#add(java.lang.Object)