// In header: <boost/date_time/date_generators.hpp>
template<typename date_type> 
class first_kday_of_month :
  public boost::date_time::year_based_generator< date_type >
{
public:
  // types
  typedef date_type::calendar_type        calendar_type;   
  typedef calendar_type::day_of_week_type day_of_week_type;
  typedef calendar_type::month_type       month_type;      
  typedef calendar_type::year_type        year_type;       
  typedef date_type::duration_type        duration_type;   
  // construct/copy/destruct
  first_kday_of_month(day_of_week_type, month_type);
  // public member functions
  virtual date_type get_date(year_type) const;
  month_type month() const;
  day_of_week_type day_of_week() const;
  virtual std::string to_string() const;
};