**Retention rule that applies:** 45 days for production systems.  

**Why:**  
- The policy dated **2026‑05** is the most recent rule that specifically mentions production systems.  
- It supersedes earlier policies (2024‑01 and 2025‑06) because it is newer and applies to the same system type.  
- Therefore, a production system today (2026‑06‑16) must retain backups for 45 days.