Returns when a time zone enters Daylight Time.
Usage depends on whether this is an absolute date, such as October 31, or a relative date, such as the last Sunday in October.
If IsDaylightAbsoluteDate is TRUE, then ignore the year.
If IsDaylightAbsoluteDate is FALSE, then use only the hours, minutes, and seconds portion of the date.
Undefined if SupportsDst is FALSE.