pub fn step_date_field(date: Date, kind: SegmentKind, delta: i32) -> DateExpand description
Step a single field of a Date by delta. Year saturates at the
jiff range and clamps the day if the new year+month no longer holds
the current day (e.g. Feb 29 → Feb 28 in non-leap years). Month
wraps within [1, 12] and clamps the day to the new month’s last
day. Day wraps within the current month — does not advance to the
next month, matching Qt QDateEdit and macOS Calendar behaviour.
Returns the input date unchanged when kind is not a date field.