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