Struct template us_dst_trait

Boost C++ Libraries

Struct template us_dst_trait

boost::date_time::us_dst_trait — Specification for daylight savings start rules in US.

Synopsis

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

template<typename date_type> 
struct us_dst_trait {
  // types
  typedef date_type::day_of_week_type                 day_of_week_type;          
  typedef date_type::month_type                       month_type;                
  typedef date_type::year_type                        year_type;                 
  typedef date_time::nth_kday_of_month< date_type >   start_rule_functor;        
  typedef date_time::first_kday_of_month< date_type > end_rule_functor;          
  typedef date_time::first_kday_of_month< date_type > start_rule_functor_pre2007;
  typedef date_time::last_kday_of_month< date_type >  end_rule_functor_pre2007;  

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

Description

This class is used to configure dst_calc_engine template typically as follows:

          using namespace boost::gregorian;
          using namespace boost::posix_time;
          typedef us_dst_trait<date> us_dst_traits;
          typedef boost::date_time::dst_calc_engine<date, time_duration, 
                                                    us_dst_traits>  
                                                    us_dst_calc;
          //calculate the 2002 transition day of USA April 7 2002
          date dst_start = us_dst_calc::local_dst_start_day(2002); 

          //calculate the 2002 transition day of USA Oct 27 2002
          date dst_end = us_dst_calc::local_dst_end_day(2002); 
                                                    
          //check if a local time is in dst or not -- posible answers
          //are yes, no, invalid time label, ambiguous
          ptime t(...some time...);  
          if (us_dst::local_is_dst(t.date(), t.time_of_day()) 
              == boost::date_time::is_not_in_dst) 
          {

          }

This generates a type suitable for the calculation of dst transitions for the United States. Of course other templates can be used for other locales.

`us_dst_trait` public static functions

static day_of_week_type start_day(year_type);

static month_type start_month(year_type y);

static day_of_week_type end_day(year_type);

static month_type end_month(year_type y);

static date_type local_dst_start_day(year_type year);

static date_type local_dst_end_day(year_type year);

```
static int dst_start_offset_minutes();
```
```
static int dst_end_offset_minutes();
```
```
static int dst_shift_length_minutes();
```