{"abstract":"Year subtraction increments age before the birthday.","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. born<=today; February 29 anniversaries are observed on February 28 in nonleap years. Exact operational definition: (date.fromisoformat(today).year-date.fromisoformat(born).year)-int(date.fromisoformat(today)<date(date.fromisoformat(today).year,date.fromisoformat(born).month,min(date.fromisoformat(born).day,calendar.monthrange(date.fromisoformat(today).year,date.fromisoformat(born).month)[1])))","contract_signature":"born, today","evaluation_group":"model-4e0a59aa013d8b04","failed_approach":"A fixed 365-day duration drifts across leap years.","family":"xn-whole-birthday-years-february-28-policy","id":"FA-6546","implementations":{"attempt":{"sha256":"62951eac008c4d756ede92d8321b9e5c307287c05445fcca1f5571e6f03878bf","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(born, today):\n    return int((date.fromisoformat(today)-date.fromisoformat(born)).days/365)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck(\"fixture 1: ('2000-06-15', '2024-06-14')\", solve(*('2000-06-15', '2024-06-14')), 23)\ncheck(\"fixture 2: ('2000-06-15', '2024-06-15')\", solve(*('2000-06-15', '2024-06-15')), 24)\ncheck(\"fixture 3: ('2000-02-29', '2023-02-28')\", solve(*('2000-02-29', '2023-02-28')), 23)\ncheck(\"fixture 4: ('2024-01-01', '2024-01-01')\", solve(*('2024-01-01', '2024-01-01')), 0)\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":"896ffb58eecec78392695c091af3a9998df7c5cbbf5ae74c0211fba5a112f636","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(born, today):\n    return date.fromisoformat(today).year-date.fromisoformat(born).year\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck(\"fixture 1: ('2000-06-15', '2024-06-14')\", solve(*('2000-06-15', '2024-06-14')), 23)\ncheck(\"fixture 2: ('2000-06-15', '2024-06-15')\", solve(*('2000-06-15', '2024-06-15')), 24)\ncheck(\"fixture 3: ('2000-02-29', '2023-02-28')\", solve(*('2000-02-29', '2023-02-28')), 23)\ncheck(\"fixture 4: ('2024-01-01', '2024-01-01')\", solve(*('2024-01-01', '2024-01-01')), 0)\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-whole-birthday-years-february-28-policy","generated_at":"2026-09-29T14:38:03.077725+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":"Year subtraction increments age before the birthday.","sha256":"e3d6771b6bc8d0749a69170ed38f6381cb1d0c7fba023a9249892503bfb5df2b","title":"Whole birthday years february 28 policy · 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":42.864,"exit_code":1,"observations":[{"actual":24,"check":"fixture 1: ('2000-06-15', '2024-06-14')","expected":23,"passed":false},{"actual":24,"check":"fixture 2: ('2000-06-15', '2024-06-15')","expected":24,"passed":true},{"actual":23,"check":"fixture 3: ('2000-02-29', '2023-02-28')","expected":23,"passed":true},{"actual":0,"check":"fixture 4: ('2024-01-01', '2024-01-01')","expected":0,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2000-06-15', '2024-06-14')\", \"actual\": 24, \"expected\": 23, \"passed\": false}, {\"check\": \"fixture 2: ('2000-06-15', '2024-06-15')\", \"actual\": 24, \"expected\": 24, \"passed\": true}, {\"check\": \"fixture 3: ('2000-02-29', '2023-02-28')\", \"actual\": 23, \"expected\": 23, \"passed\": true}, {\"check\": \"fixture 4: ('2024-01-01', '2024-01-01')\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":45.74,"exit_code":1,"observations":[{"actual":24,"check":"fixture 1: ('2000-06-15', '2024-06-14')","expected":23,"passed":false},{"actual":24,"check":"fixture 2: ('2000-06-15', '2024-06-15')","expected":24,"passed":true},{"actual":23,"check":"fixture 3: ('2000-02-29', '2023-02-28')","expected":23,"passed":true},{"actual":0,"check":"fixture 4: ('2024-01-01', '2024-01-01')","expected":0,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ('2000-06-15', '2024-06-14')\", \"actual\": 24, \"expected\": 23, \"passed\": false}, {\"check\": \"fixture 2: ('2000-06-15', '2024-06-15')\", \"actual\": 24, \"expected\": 24, \"passed\": true}, {\"check\": \"fixture 3: ('2000-02-29', '2023-02-28')\", \"actual\": 23, \"expected\": 23, \"passed\": true}, {\"check\": \"fixture 4: ('2024-01-01', '2024-01-01')\", \"actual\": 0, \"expected\": 0, \"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."}}