Dates and freshness

effectiveDate is the publication date of a board (YYYY-MM-DD, UTC). Cross-bank comparisons are pinned to a single date so no bank competes with a stale quote: today's board when one exists, otherwise the most recent earlier one — on a Sunday that reads as Saturday. asOf is a different thing: the last time any bank in the response was successfully scraped.

Where an endpoint keeps banks that missed the current board, they are ordered last and flagged isStale.