Function dst_transitions_for_year 

pub fn dst_transitions_for_year(
    std_offset: i32,
    dst_offset: i32,
    start: DstRule,
    end: DstRule,
    year: i64,
) -> [ZoneTransition; 2]

The two UTC transitions for year of a zone with a regular DST schedule: spring-forward (std_offset → dst_offset) at start, fall-back (dst_offset → std_offset) at end. Each rule’s time_seconds is wall-clock local in the offset in effect just before the transition.