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## Class template day_calc_dst_rule

boost::date_time::day_calc_dst_rule — Canonical form for a class that provides day rule calculation.

## Synopsis

    // In header: <boost/date_time/dst_transition_generators.hpp>

    template<typename spec>
    class day_calc_dst_rule :
      public boost::date_time::dst_day_calc_rule< spec::date_type >
    {
    public:
      // types
      typedef spec::date_type      date_type;
      typedef date_type::year_type year_type;
      typedef spec::start_rule     start_rule;
      typedef spec::end_rule       end_rule;

      // construct/copy/destruct
      day_calc_dst_rule(start_rule, end_rule);

      // public member functions
      virtual date_type start_day(year_type) const;
      virtual std::string start_rule_as_string() const;
      virtual date_type end_day(year_type) const;
      virtual std::string end_rule_as_string() const;
    };

## Description

This class is used to generate specific sets of dst rules

### Template Parameters

1.     typename spec

   Provides a specifiction of the function object types used to generate start and end days of daylight savings as well as the date type.

### `day_calc_dst_rule` public construct/copy/destruct

1.     day_calc_dst_rule(start_rule dst_start, end_rule dst_end);

### `day_calc_dst_rule` public member functions

1.     virtual date_type start_day(year_type y) const;

2.     virtual std::string start_rule_as_string() const;

3.     virtual date_type end_day(year_type y) const;

4.     virtual std::string end_rule_as_string() const;