code: private long getTotalTime(ProjectCalendarDateRanges exception)
     {
        long total = 0;
        for (DateRange range : exception)
        {
           total += getTime(range.getStart(), range.getEnd());
        }
        return (total);
     }
docs: Retrieves the amount of working time represented by
  a calendar exception.
  
  @param exception calendar exception
  @return length of time in milliseconds