Class template dst

Class template dst_calculator

boost::date_time::dst_calculator — Dynamic class used to caluclate dst transition information.

Synopsis

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

template<typename date_type_, typename time_duration_type_> 
class dst_calculator {
public:
  // types
  typedef time_duration_type_ time_duration_type;
  typedef date_type_          date_type;         

  // public static functions
  static time_is_dst_result 
  process_local_dst_start_day(const time_duration_type &, unsigned int, long);
  static time_is_dst_result 
  process_local_dst_end_day(const time_duration_type &, unsigned int, long);
  static time_is_dst_result 
  local_is_dst(const date_type &, const time_duration_type &, 
               const date_type &, const time_duration_type &, 
               const date_type &, const time_duration_type &, 
               const time_duration_type &);
  static time_is_dst_result 
  local_is_dst(const date_type &, const time_duration_type &, 
               const date_type &, unsigned int, const date_type &, 
               unsigned int, long);
};

Description

`dst_calculator` public static functions

static time_is_dst_result 
process_local_dst_start_day(const time_duration_type & time_of_day, 
                            unsigned int dst_start_offset_minutes, 
                            long dst_length_minutes);

Check the local time offset when on dst start day.

On this dst transition, the time label between the transition boundary and the boudary + the offset are invalid times. If before the boundary then still not in dst.

Parameters:

`dst_length_minutes`	Number of minutes to adjust clock forward
`dst_start_offset_minutes`	Local day offset for start of dst
`time_of_day`	Time offset in the day for the local time

```
static time_is_dst_result 
process_local_dst_end_day(const time_duration_type & time_of_day, 
                          unsigned int dst_end_offset_minutes, 
                          long dst_length_minutes);
```
Check the local time offset when on the last day of dst.
This is the calculation for the DST end day. On that day times prior to the conversion time - dst_length (1 am in US) are still in dst. Times between the above and the switch time are ambiguous. Times after the start_offset are not in dst.

Parameters:

dst_end_offset_minutes

Local time of day for end of dst

time_of_day

Time offset in the day for the local time

static time_is_dst_result 
local_is_dst(const date_type & current_day, 
             const time_duration_type & time_of_day, 
             const date_type & dst_start_day, 
             const time_duration_type & dst_start_offset, 
             const date_type & dst_end_day, 
             const time_duration_type & dst_end_offset, 
             const time_duration_type & dst_length);

Calculates if the given local time is dst or not.

Determines if the time is really in DST or not. Also checks for invalid and ambiguous.

Parameters:

`current_day`	The day to check for dst
`dst_end_day`	Ending day of dst for the given locality
`dst_end_offset`	Time offset within day given in dst for dst boundary
`dst_start_day`	Starting day of dst for the given locality
`dst_start_offset`	Time offset within day for dst boundary
`time_of_day`	Time offset within the day to check

static time_is_dst_result 
local_is_dst(const date_type & current_day, 
             const time_duration_type & time_of_day, 
             const date_type & dst_start_day, 
             unsigned int dst_start_offset_minutes, 
             const date_type & dst_end_day, 
             unsigned int dst_end_offset_minutes, long dst_length_minutes);

Calculates if the given local time is dst or not.

Determines if the time is really in DST or not. Also checks for invalid and ambiguous.

Parameters:

`current_day`	The day to check for dst
`dst_end_day`	Ending day of dst for the given locality
`dst_end_offset_minutes`	Offset within day given in dst for dst boundary (eg 120 for US which is 02:00:00)
`dst_length_minutes`	Length of dst adjusment (eg: 60 for US)
`dst_start_day`	Starting day of dst for the given locality
`dst_start_offset_minutes`	Offset within day for dst boundary (eg 120 for US which is 02:00:00)
`time_of_day`	Time offset within the day to check