anchor.diff:    static final _allowed = <String>{
       'hour',
       'day',
  +    'week',
       'month',
       'year',
       'term',
  
positive.code:       case 'day':
          out = day;
          break;
        case 'month':
          out = month;
          break;
  
negative.code: 
    static const hour = TimeAggregation._internal('hour');
    static const day = TimeAggregation._internal('day');
    static const week = TimeAggregation._internal('week');
    static const month = TimeAggregation._internal('month');
    static const year = TimeAggregation._internal('year');
    static const term = TimeAggregation._internal('term');
  