template<typename date_type> 
struct acst_dst_trait {
  // types
  typedef date_type::day_of_week_type                day_of_week_type;  
  typedef date_type::month_type                      month_type;        
  typedef date_time::last_kday_of_month< date_type > start_rule_functor;
  typedef date_time::last_kday_of_month< date_type > end_rule_functor;  

  // public static functions
  day_of_week_type start_day() ;
  month_type start_month() ;
  day_of_week_type end_day() ;
  month_type end_month() ;
  int dst_start_offset_minutes() ;
  int dst_end_offset_minutes() ;
  int dst_shift_length_minutes() ;
};