TzSpecificLocalTimeToSystemTime during DT -< ST transition

It seems to me there is some ambiguity during the transition between Daylight time to Standard time for example in the US at 2:00 AM DT on 11/1 Daylight time ended and Standard time began the time now being 1:00 AM ST. This means that a time of 1:30 is meaningless unless it i开发者_C百科s qualified as ST or DT. So, how can TzSpecificLocalTimeToSystemTime convert this time?

It can guess, at best. Since SYSTEMTIME structure lacks DST bit, there are indeed inherently ambiguous periods.