Because newest by publication or indexing time is not necessarily effective now. A policy approved on 20 September may be published immediately but take effect on 1 October. The search index sees a fresh and highly relevant document. The assistant uses it to answer a question about a transaction on 28 September. Retrieval did its ordinary relevance job and still selected the wrong rule for the decision time.

I would keep at least the policy version, effective-from and effective-until times, publication state and source authority with each indexed passage. The answer needs an explicit as-of time. For “what applies to this transaction,” that may be the transaction time under the organization's rules, not the current clock. A query about a historical case can require a different version from a question about a future plan. PostgreSQL's range-type documentation describes temporal ranges and nonoverlap constraints. Those are useful implementation tools for the authoritative rule table, but a vector index alone does not become a policy engine just because each chunk has a date.

Filter or validate candidates against the effective interval before a rule is used for an action. Do it in the trusted service against the authoritative version if the decision is consequential. Handle timezone and half-open interval boundaries explicitly. If two conflicting versions claim the same time or no authoritative version covers it, return a conflict or ask for review instead of letting relevance score pick the winner. Cite the version and applicable interval in the answer so a reader can audit the choice.

There is a second clock too. When did our system learn that a correction was made? A rule corrected on 5 October with a retroactive effective date of 1 September may change today's answer to “what rule was legally in force on 28 September,” while leaving a separate audit question about what the agent knew on 28 September. Keep source history if both questions matter. Which policy source wins when the newer indexed copy is wrong? addresses a newer indexed copy contradicting its authoritative source. This case can have two valid source versions. The error is choosing by freshness when the query is about effective time.