// In header: <boost/date_time/gregorian/greg_facet.hpp>

struct greg_facet_config {
  // types
  typedef boost::gregorian::greg_month     month_type;        
  typedef boost::date_time::special_values special_value_enum;
  typedef boost::gregorian::months_of_year month_enum;        
  typedef boost::date_time::weekdays       weekday_enum;      
};