code: public final void setTimeZone(final TimeZone timeZone) {
          for (final Period period : this) {
              period.setTimeZone(timeZone);
          }
          this.timezone = timeZone;
          this.utc = false;
      }
docs: Applies the specified timezone to all dates in the list.
  All dates added to this list will also have this timezone
  applied.
  @param timeZone the timezone for the period list