{"abstract":"Month start replaces quarter start.","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. Calendar quarter start. Exact operational definition: date(date.fromisoformat(text).year,3*((date.fromisoformat(text).month-1)//3)+1,1).isoformat()","contract_signature":"text","evaluation_group":"model-a22fc409d58ce131","failed_approach":"The quarter division shifts terminal months into the following quarter.","family":"xn-calendar-quarter-start","id":"FA-6526","implementations":{"attempt":{"sha256":"77d0a1a7a07007c3fc3166501cb60bc27b7775b435ce5b40a23f42b93f8021b1","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(date.fromisoformat(text).year,3*(date.fromisoformat(text).month//3)+1,1).isoformat() if date.fromisoformat(text).month<12 else date(date.fromisoformat(text).year+1,1,1).isoformat()\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck(\"fixture 1: ('2024-03-31',)\", solve(*('2024-03-31',)), '2024-01-01')\ncheck(\"fixture 2: ('2024-04-15',)\", solve(*('2024-04-15',)), '2024-04-01')\ncheck(\"fixture 3: ('2024-12-31',)\", solve(*('2024-12-31',)), '2024-10-01')\ncheck(\"fixture 4: ('2024-01-01',)\", solve(*('2024-01-01',)), '2024-01-01')\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":"6521ef9b633abcf232e266557ed37b6c4d1ed69b9bc6b2cfb75e591ab3ed81e4","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(date.fromisoformat(text).year,date.fromisoformat(text).month,1).isoformat()\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck(\"fixture 1: ('2024-03-31',)\", solve(*('2024-03-31',)), '2024-01-01')\ncheck(\"fixture 2: ('2024-04-15',)\", solve(*('2024-04-15',)), '2024-04-01')\ncheck(\"fixture 3: ('2024-12-31',)\", solve(*('2024-12-31',)), '2024-10-01')\ncheck(\"fixture 4: ('2024-01-01',)\", solve(*('2024-01-01',)), '2024-01-01')\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-calendar-quarter-start","generated_at":"2026-09-29T14:38:02.940997+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":"Month start replaces quarter start.","sha256":"c9e9a37e66aebb5a369f6c0d6a36f72769bfda3c96fe6649cc7758c8706c09a9","title":"Calendar quarter start · 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":43.205,"exit_code":1,"observations":[{"actual":"2024-04-01","check":"fixture 1: ('2024-03-31',)","expected":"2024-01-01","passed":false},{"actual":"2024-04-01","check":"fixture 2: ('2024-04-15',)","expected":"2024-04-01","passed":true},{"actual":"2025-01-01","check":"fixture 3: ('2024-12-31',)","expected":"2024-10-01","passed":false},{"actual":"2024-01-01","check":"fixture 4: ('2024-01-01',)","expected":"2024-01-01","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2024-03-31',)\", \"actual\": \"2024-04-01\", \"expected\": \"2024-01-01\", \"passed\": false}, {\"check\": \"fixture 2: ('2024-04-15',)\", \"actual\": \"2024-04-01\", \"expected\": \"2024-04-01\", \"passed\": true}, {\"check\": \"fixture 3: ('2024-12-31',)\", \"actual\": \"2025-01-01\", \"expected\": \"2024-10-01\", \"passed\": false}, {\"check\": \"fixture 4: ('2024-01-01',)\", \"actual\": \"2024-01-01\", \"expected\": \"2024-01-01\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.653,"exit_code":1,"observations":[{"actual":"2024-03-01","check":"fixture 1: ('2024-03-31',)","expected":"2024-01-01","passed":false},{"actual":"2024-04-01","check":"fixture 2: ('2024-04-15',)","expected":"2024-04-01","passed":true},{"actual":"2024-12-01","check":"fixture 3: ('2024-12-31',)","expected":"2024-10-01","passed":false},{"actual":"2024-01-01","check":"fixture 4: ('2024-01-01',)","expected":"2024-01-01","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2024-03-31',)\", \"actual\": \"2024-03-01\", \"expected\": \"2024-01-01\", \"passed\": false}, {\"check\": \"fixture 2: ('2024-04-15',)\", \"actual\": \"2024-04-01\", \"expected\": \"2024-04-01\", \"passed\": true}, {\"check\": \"fixture 3: ('2024-12-31',)\", \"actual\": \"2024-12-01\", \"expected\": \"2024-10-01\", \"passed\": false}, {\"check\": \"fixture 4: ('2024-01-01',)\", \"actual\": \"2024-01-01\", \"expected\": \"2024-01-01\", \"passed\": true}], \"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."}}