[Boost-bugs] [Boost C++ Libraries] #6045: Date/Time: dst_calculator::local_is_dst doesn't deal with DST changeover at end of day

Subject: [Boost-bugs] [Boost C++ Libraries] #6045: Date/Time: dst_calculator::local_is_dst doesn't deal with DST changeover at end of day
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-10-20 23:26:33

#6045: Date/Time: dst_calculator::local_is_dst doesn't deal with DST changeover at
end of day
------------------------------------------------+---------------------------
 Reporter:  Matt Adam <matt.adam@…>             |       Owner:         
     Type:  Bugs                                |      Status:  new    
Milestone:  To Be Determined                    |   Component:  None   
  Version:  Boost 1.47.0                        |    Severity:  Problem
 Keywords:                                      |  
------------------------------------------------+---------------------------
 Hello boosters,

 dst_calculator::local_is_dst assumes that the hour lost in the "forward"
 DST changeover (in Spring, when DST begins) fully occurs within a single
 day.  If your time zone rule specifies that DST begins at 23:59:99.999 on
 October 15th, with a duration of an hour, and you attempt to create a
 ptime for 00:00:00.000 on October 16th, it will succeed even though it
 ought to return invalid_time_label.

 I admit that this seems like an odd case, and personally I would expect
 all DST offsets to be in the 0h-3h range.  However if you are creating
 custom time zones based on the win32 time zone information, the
 GetTimeZoneInformation API returns a TIME_ZONE_INFORMATION struct with
 values returned a millisecond before midnight.  Specifically this happens
 with Brasilian standard/daylight time.

 For now I am "cleaning up" these odd values returned from windows, but
 boost probably should do this calculation correctly to begin with.

 I can provide a repro case if need be, although I think the behaviour of
 the code in question is pretty clear.

 Thanks,

 Matt Adam

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6045>
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