Calculate secondary-progressed planets with natal context

Day-for-year secondary-progressed PLANETS only. Required target>=birth instant; all civil dates 1800–2200, times known, UTC defaults and DST rejection. Fixed365.2421904-day year in TT. Returned angles/houses are explicitly natal context, never progressed. No progressed angles, houses, aspects, nodes, speed or arbitrary year model. All admitted attempts use one standard quota unit, including free plans. No practitioner sign-off is claimed.

Each admitted request reserves one monthly usage unit before route validation or engine work; 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.