Show whether electional results change with the sampling anchor

Evaluates the caller's existing electional predicates once on a fixed 15-minute, start-inclusive UTC grid spanning at most seven days. The same samples are projected onto both possible 30-minute phases and all four possible 60-minute phases, each measured from the request start. It returns every finest-grid sample, every observed matching run, each phase's exact matching samples, and exact witnesses for runs detected by some anchors but missed by others. A run is only a contiguous sequence of matching 15-minute samples; boundaries are not interpolated. This is sampled evidence, not continuous-time proof, probability, statistical confidence, ranking, recommendation, interpretation, or prediction. One standard quota unit per admitted request; failed or timed-out admitted attempts are not refunded. Do not automatically retry. Historical mode uses an explicit BCE/CE date object and UT1 conventions. Its response is the versioned historical envelope, not the modern UTC envelope. Read result for calculation fields and metadata for limits and uncertainty.