Class template dst

Class template dst_calculator

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

Synopsis

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
  time_is_dst_result 
  process_local_dst_start_day(const time_duration_type &, unsigned int, long) ;
  time_is_dst_result 
  process_local_dst_end_day(const time_duration_type &, unsigned int, long) ;
  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 &) ;
  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

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) ;

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

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) ;

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

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_minutes) ;

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

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) ;

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