{"abstract":"The weekday origin remains Monday.","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. Sunday zero weekday. Exact operational definition: (date.fromisoformat(text).weekday()+1)%7","contract_signature":"text","evaluation_group":"model-9a138b955b4a8a04","failed_approach":"Sunday retains ISO value seven instead of zero.","family":"xn-sunday-zero-weekday","id":"FA-6501","implementations":{"attempt":{"sha256":"db00e0a90565a24bba862852f8b3efbc9f53aa5add50acfb737b07d95877edb2","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).isoweekday()\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',)), 0)\ncheck(\"fixture 3: ('2024-02-29',)\", solve(*('2024-02-29',)), 4)\ncheck(\"fixture 4: ('2024-01-06',)\", solve(*('2024-01-06',)), 6)\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":"215003776f1a33a1f7ad22dbe4221a2d2db8417d867515aed1fb1536f8355e19","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',)), 0)\ncheck(\"fixture 3: ('2024-02-29',)\", solve(*('2024-02-29',)), 4)\ncheck(\"fixture 4: ('2024-01-06',)\", solve(*('2024-01-06',)), 6)\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-sunday-zero-weekday","generated_at":"2026-09-29T14:38:02.543265+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":"The weekday origin remains Monday.","sha256":"b3c2832e3e3dca6925b8d35e7639c79639074d9ab93e326115c52ff1aacbb3a0","title":"Sunday zero weekday · 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":43.169,"exit_code":1,"observations":[{"actual":1,"check":"fixture 1: ('2024-01-01',)","expected":1,"passed":true},{"actual":7,"check":"fixture 2: ('2024-01-07',)","expected":0,"passed":false},{"actual":4,"check":"fixture 3: ('2024-02-29',)","expected":4,"passed":true},{"actual":6,"check":"fixture 4: ('2024-01-06',)","expected":6,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2024-01-01',)\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"fixture 2: ('2024-01-07',)\", \"actual\": 7, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3: ('2024-02-29',)\", \"actual\": 4, \"expected\": 4, \"passed\": true}, {\"check\": \"fixture 4: ('2024-01-06',)\", \"actual\": 6, \"expected\": 6, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.983,"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":0,"passed":false},{"actual":3,"check":"fixture 3: ('2024-02-29',)","expected":4,"passed":false},{"actual":5,"check":"fixture 4: ('2024-01-06',)","expected":6,"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\": 0, \"passed\": false}, {\"check\": \"fixture 3: ('2024-02-29',)\", \"actual\": 3, \"expected\": 4, \"passed\": false}, {\"check\": \"fixture 4: ('2024-01-06',)\", \"actual\": 5, \"expected\": 6, \"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."}}