Struct template us_dst_trait

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Struct template us_dst_trait

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

Synopsis

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_time::first_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() ;
};

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

```
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() ;
```

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