half-open-intervals

Date: 2026-09-10. Status: implemented.

Decision. A record is valid for introduced_on <= date < deleted_on, with null deletion open-ended. Same-day records are retained but never match an as-of query.

Reason. Eight small-user records reuse 18 February 2026 as both a deletion and a reintroduction date, so a closed-interval rule would report overlaps that are not there.

Evidence. SPD 2026/2 news bulletin, retrospective split correction for AB31 5AS, AB54 7NS, FK14 7JX and KA6 6EY.

Columns (3): deleted_on, introduced_on, is_current