Updates a time condition in place; fields you omit keep their current values, while conditions is replaced wholesale by whatever array you send. Send expected_update_date to avoid clobbering a concurrent change — a mismatch fails with 409 and code: "stale" instead of writing. A condition owned by a call flow cannot be edited here and returns 409. Sending no body at all (or a body that is not valid JSON) is not an error: it instead drops expired holiday rules from the live routing, leaving the stored conditions array untouched, and returns {"success": true}. The record and its routing entry are written separately, so a failure part-way through leaves no rollback.