docs: @SuppressWarnings( "fallthrough" )
      private void rollup() {
          DateTime now = timeFactory.create();
          Window largest = null;
          for (DurationHistory history : durations.values()) {
              largest = history.rollup();
          }
          for (ValueHistory history : values.values()) {
              largest = history.rollup();
          }
          if ( largest == null ) return;
          // Note that we do expect to fall through, as the 'largest' represents the largest window that was changed,
          // while all smaller windows were also changed ...
          switch (largest) {
              case PREVIOUS_52_WEEKS:
                  this.weeksStartTime.set(now);
                  // fall through!!
              case PREVIOUS_7_DAYS:
                  this.daysStartTime.set(now);
                  // fall through!!
              case PREVIOUS_24_HOURS:
                  this.hoursStartTime.set(now);
                  // fall through!!
              case PREVIOUS_60_MINUTES:
                  this.minutesStartTime.set(now);
                  // fall through!!
              case PREVIOUS_60_SECONDS:
                  this.secondsStartTime.set(now);
          }
      }