lunar-return-1.0.0 targets the saved natal tropical geocentric Moon longitude. It requires a timezone-aware anchor and a previous or next direction, excludes the anchor itself by one second, and searches no more than 35 days.

Deterministic solver contract

• Swiss Ephemeris swe_calc_ut supplies geocentric tropical Moon longitude in Universal Time.
• The search scans chronologically in three-hour intervals and accepts only the increasing signed-longitude target crossing.
• Bisection refines the bracket until its time width is below one millisecond.
• The response preserves anchor, direction, UTC and local result times, target and calculated longitudes, residual arcseconds, iteration count, bracket width, search limit, location policy, and the full return chart.
• A previous result must precede the anchor and a next result must follow it.

Regression evidence

The engine fixtures require deterministic repetition, strict directionality, a previous-to-next interval between 20 and 35 days, sub-milliarcsecond residual, all seven traditional planets, target equality in the returned Moon, authorization, timezone validation, and location invariance of the recurrence instant with different angles.

Scope and source boundary

Swiss Ephemeris documents the astronomical longitude and speed calculation. Stelliums governs the search algorithm, chart construction, location policy, provenance, and QA. This release does not use that technical source as evidence for a complete ancient monthly interpretation doctrine.