{"abstract":"A zero-based weekday is returned where Monday is one.","category":"Calendar arithmetic","checks":4,"contract":"Valid ISO Gregorian dates in years 1 through 9999; generated dates must remain in that range. Month is 1 through 12 and zero-based weekday is Monday 0 through Sunday 6 unless the output convention says otherwise. Iso weekday monday one. Exact operational definition: date.fromisoformat(text).isoweekday()","contract_signature":"text","evaluation_group":"model-f0dcfb8a2196d75b","failed_approach":"Modulo maps Sunday to zero rather than seven.","family":"xn-iso-weekday-monday-one","id":"FA-6496","implementations":{"attempt":{"sha256":"73a35c460ebeed62516e71405fef11242404d9bb6b3640c91362ffbd1fbf8a65","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(text):\n    return (date.fromisoformat(text).weekday()+1)%7\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck(\"fixture 1: ('2024-01-01',)\", solve(*('2024-01-01',)), 1)\ncheck(\"fixture 2: ('2024-01-07',)\", solve(*('2024-01-07',)), 7)\ncheck(\"fixture 3: ('2024-02-29',)\", solve(*('2024-02-29',)), 4)\ncheck(\"fixture 4: ('2023-12-31',)\", solve(*('2023-12-31',)), 7)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"91b67e83f5326842f0133bd2ffd98aa2b470c0bc4c453391a83a2fdb32d5d905","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(text):\n    return date.fromisoformat(text).weekday()\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck(\"fixture 1: ('2024-01-01',)\", solve(*('2024-01-01',)), 1)\ncheck(\"fixture 2: ('2024-01-07',)\", solve(*('2024-01-07',)), 7)\ncheck(\"fixture 3: ('2024-02-29',)\", solve(*('2024-02-29',)), 4)\ncheck(\"fixture 4: ('2023-12-31',)\", solve(*('2023-12-31',)), 7)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xn-iso-weekday-monday-one","generated_at":"2026-09-29T14:38:02.457237+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Calendar conventions results depend on the stated convention.","root_cause":"A zero-based weekday is returned where Monday is one.","sha256":"5797a0c45849483bd23bf3d446ad7476fb3b92ce1504015665f73ffbaab95877","title":"Iso weekday monday one · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":44.655,"exit_code":1,"observations":[{"actual":1,"check":"fixture 1: ('2024-01-01',)","expected":1,"passed":true},{"actual":0,"check":"fixture 2: ('2024-01-07',)","expected":7,"passed":false},{"actual":4,"check":"fixture 3: ('2024-02-29',)","expected":4,"passed":true},{"actual":0,"check":"fixture 4: ('2023-12-31',)","expected":7,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2024-01-01',)\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 2: ('2024-01-07',)\", \"actual\": 0, \"expected\": 7, \"passed\": false}, {\"check\": \"fixture 3: ('2024-02-29',)\", \"actual\": 4, \"expected\": 4, \"passed\": true}, {\"check\": \"fixture 4: ('2023-12-31',)\", \"actual\": 0, \"expected\": 7, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":113.96,"exit_code":1,"observations":[{"actual":0,"check":"fixture 1: ('2024-01-01',)","expected":1,"passed":false},{"actual":6,"check":"fixture 2: ('2024-01-07',)","expected":7,"passed":false},{"actual":3,"check":"fixture 3: ('2024-02-29',)","expected":4,"passed":false},{"actual":6,"check":"fixture 4: ('2023-12-31',)","expected":7,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2024-01-01',)\", \"actual\": 0, \"expected\": 1, \"passed\": false}, {\"check\": \"fixture 2: ('2024-01-07',)\", \"actual\": 6, \"expected\": 7, \"passed\": false}, {\"check\": \"fixture 3: ('2024-02-29',)\", \"actual\": 3, \"expected\": 4, \"passed\": false}, {\"check\": \"fixture 4: ('2023-12-31',)\", \"actual\": 6, \"expected\": 7, \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}