id summary reporter owner description type status milestone component version severity resolution keywords cc 6045 Date/Time: dst_calculator::local_is_dst doesn't deal with DST changeover at end of day Matt Adam az_sw_dude "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" Bugs new To Be Determined date_time Boost 1.47.0 Problem