hen call dst_rules::local_is_dst with the non adjust local time. The results of this function will either unabiguously decide that the initial local time is in dst or return an illegal or ambiguous result. An illegal result only occurs at the end of dst (where labels are skipped) and indicates that dst has ended. An ambiguous result means that we need to recheck by making a dst adjustment and then rechecking. If the dst offset is added to the utc time and the recheck proves non-ambiguous then we are past th