code: protected BooleanQuery.Builder appendDateCreatedFilter(BooleanQuery.Builder filter, long startTime, long endTime) {
  
          // create special optimized sub-filter for the date last modified search
          Query dateFilter = createDateRangeFilter(CmsSearchField.FIELD_DATE_CREATED_LOOKUP, startTime, endTime);
          if (dateFilter != null) {
              // extend main filter with the created date filter
              filter.add(new BooleanClause(dateFilter, BooleanClause.Occur.MUST));
          }
  
          return filter;
      }
docs: Appends a date of creation filter to the given filter clause that matches the
  given time range.<p>
  
  If the start time is equal to {@link Long#MIN_VALUE} and the end time is equal to {@link Long#MAX_VALUE}
  than the original filter is left unchanged.<p>
  
  The original filter parameter is extended and also provided as return value.<p>
  
  @param filter the filter to extend
  @param startTime start time of the range to search in
  @param endTime end time of the range to search in
  
  @return the extended filter clause