{
  "vercy": "1.0-draft",
  "publication": {
    "status": "research-draft",
    "adjudicationStatus": "unreviewed",
    "publishableCanonical": false,
    "generatedAt": "2026-09-14T02:27:14Z",
    "providers": [
      "Claude"
    ],
    "breadth": "written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify",
    "pass": 2,
    "wave": 4,
    "engine": "claude",
    "enrichment": {
      "pass": 3,
      "engine": "claude",
      "producedAt": "2026-10-06T11:00:00Z",
      "ingestedAt": "2026-10-06T07:42:42+00:00",
      "fields": [
        "agent_conduct",
        "ethics",
        "owners"
      ]
    },
    "revisions": [
      {
        "at": "2026-10-06T22:50:24+00:00",
        "engine": "codex",
        "fields": [
          "definition"
        ],
        "answering_review": "fa3e088d1061f277d137813d361c6a2e1eb76ed079a840326c9215c7731c39ec"
      }
    ],
    "gate": {
      "passed": true,
      "version": "1.0",
      "at": "2026-10-07T10:10:30+00:00",
      "evidence": [
        "completeness 1.00",
        "sense: Wikidata description",
        "2 live sources",
        "review by codex: pass"
      ]
    }
  },
  "metaModel": {
    "id": "THING-Q37096",
    "registryId": "vr.tr.february-30",
    "name": "February 30",
    "version": "0.2.0-wave.4",
    "entryKind": "thing",
    "family": "Thing Registry",
    "domain": [
      "XCT.TME"
    ],
    "status": "research-draft"
  },
  "canonicalUrl": "https://ver.cy/models/thing/q37096/",
  "model": {
    "registry_id": "vr.tr.february-30",
    "name": "February 30",
    "purpose": "Let an agent explain February 30, relay why it does not normally exist, the Swedish 1712 case and Soviet calendar experiments and its use as an impossible date from calendar history sources, and distinguish it from February 29, leap years, other calendars and ordinary invalid dates.",
    "definition": "February 30 is a date that does not exist in the standard Gregorian or Julian calendars, since February has 28 days, or 29 in a leap year. Sweden used February 30 in 1712 as an exceptional date during a calendar transition, but Soviet calendar experiments did not establish an actual February 30. It is also used as a deliberately impossible date in computing tests and fiction, rather than a real recurring Gregorian date.",
    "what_it_is_for": "A non-existent or historically exceptional calendar date.",
    "affordances": [
      "explain why it does not exist",
      "relay the Swedish and Soviet cases",
      "relay its use as an impossible date",
      "distinguish related concepts"
    ],
    "distinguishing_features": [
      "Normally invalid",
      "Rare historical cases",
      "Calendar curiosity",
      "Used as impossible date"
    ],
    "appearance": "Not a physical object; a date label that is normally invalid.",
    "visual_identification": [
      "A normally non-existent date, 30 February",
      "February 30",
      "February 29 exists in leap years; leap years add a day; other calendars have different months; ordinary invalid dates are simple errors"
    ],
    "physical_properties": [
      {
        "quantity": "Sweden",
        "typical_range": "30 February 1712",
        "unit": "date",
        "note": "calendar realignment"
      },
      {
        "quantity": "February length",
        "typical_range": "28 or 29 days",
        "unit": "note",
        "note": ""
      },
      {
        "quantity": "registry parent",
        "typical_range": "30th day of a month",
        "unit": "note",
        "note": ""
      }
    ],
    "families_and_kinds": [
      "the Swedish 1712 case",
      "Soviet calendar experiments",
      "impossible-date usage"
    ],
    "related_models": [
      {
        "relation": "is a kind of",
        "target": "calendar date",
        "why": "in registry terms, non-standard"
      },
      {
        "relation": "is contrasted with",
        "target": "February 29",
        "why": ""
      },
      {
        "relation": "is contrasted with",
        "target": "leap year",
        "why": ""
      },
      {
        "relation": "is related to",
        "target": "calendar reform",
        "why": ""
      }
    ],
    "identifiers": [],
    "standards_and_regulation": [
      "Gregorian calendar rules",
      "ISO 8601 date validity"
    ],
    "failure_modes_and_hazards": [
      "Treating February 30 as a normal date",
      "Date validation errors in software",
      "Confusing calendar history"
    ],
    "in_scope": [],
    "out_of_scope": [],
    "characteristics": [],
    "agent_conduct": {
      "may": [
        "Reject February 30 as an invalid date when validating Gregorian or Julian input.",
        "Explain the historical cases in which a February 30 was used, citing sources."
      ],
      "must_not": [
        "Silently roll February 30 over to a March date when storing records.",
        "Accept February 30 in legal, medical or financial records without flagging it.",
        "Present the historical cases as evidence that February 30 is a normal date.",
        "Schedule payments, deadlines or doses on a date that does not exist."
      ],
      "requires_human": [
        "Correcting a record that carries February 30 as a date of birth or of a legal event."
      ]
    },
    "ethics": {
      "considerations": [
        "Invalid dates in official records can block people from services or benefits.",
        "Software that mishandles dates can cause missed obligations."
      ],
      "affected_parties": [
        "People whose records carry invalid dates",
        "Users of scheduling systems",
        "Record keepers"
      ]
    },
    "owners": {
      "steward": "Nobody owns it; calendar standards bodies and record keepers decide how invalid dates are handled.",
      "master_systems": []
    }
  },
  "sources": [
    {
      "id": "wikidata",
      "title": "Wikidata item Q37096: February 30",
      "url": "https://www.wikidata.org/wiki/Q37096",
      "url_status": "live",
      "what_it_supports": "identity and sense of the item",
      "checked_by": "wikidata-api"
    },
    {
      "id": "wikipedia-en",
      "title": "Wikipedia: February 30",
      "url": "https://en.wikipedia.org/wiki/February_30",
      "url_status": "live",
      "what_it_supports": "general description of the item",
      "checked_by": "wikidata-api sitelink"
    }
  ],
  "structure": {
    "bundles": [
      {
        "id": "understand",
        "name": "Understand",
        "description": "What February 30 is.",
        "rationale": "Definition.",
        "layers": [
          {
            "id": "definition",
            "name": "Definition",
            "description": "Definition.",
            "findings": [
              {
                "id": "definition-finding",
                "name": "Definition",
                "description": "Definition.",
                "questions": [
                  {
                    "text": "What is February 30, and how does it differ from February 29, leap years, other calendars and ordinary invalid dates?",
                    "kind": "definition"
                  },
                  {
                    "text": "Is the question about calendar history or software date validation?",
                    "kind": "boundary"
                  }
                ]
              }
            ]
          },
          {
            "id": "cases",
            "name": "Cases",
            "description": "Historical cases.",
            "findings": [
              {
                "id": "cases-finding",
                "name": "Cases",
                "description": "Cases.",
                "questions": [
                  {
                    "text": "What were the Swedish 1712 and Soviet calendar cases?",
                    "kind": "definition"
                  },
                  {
                    "text": "Which entry fits calendar reform?",
                    "kind": "action"
                  }
                ]
              }
            ]
          }
        ]
      },
      {
        "id": "calendar",
        "name": "Calendar",
        "description": "Calendar rules.",
        "rationale": "Sources.",
        "layers": [
          {
            "id": "february",
            "name": "February",
            "description": "Length of February.",
            "findings": [
              {
                "id": "february-finding",
                "name": "February",
                "description": "February.",
                "questions": [
                  {
                    "text": "Why does February have 28 or 29 days?",
                    "kind": "provenance"
                  },
                  {
                    "text": "Which references are standard?",
                    "kind": "provenance"
                  }
                ]
              }
            ]
          },
          {
            "id": "leap",
            "name": "Leap",
            "description": "Leap years.",
            "findings": [
              {
                "id": "leap-finding",
                "name": "Leap",
                "description": "Leap.",
                "questions": [
                  {
                    "text": "How do leap years add February 29?",
                    "kind": "provenance"
                  },
                  {
                    "text": "Which entry fits leap year?",
                    "kind": "action"
                  }
                ]
              }
            ]
          }
        ]
      },
      {
        "id": "history",
        "name": "History",
        "description": "History.",
        "rationale": "Sources.",
        "layers": [
          {
            "id": "sweden",
            "name": "Sweden",
            "description": "Swedish 1712 case.",
            "findings": [
              {
                "id": "sweden-finding",
                "name": "Sweden",
                "description": "Sweden.",
                "questions": [
                  {
                    "text": "Why did Sweden have a 30 February in 1712?",
                    "kind": "provenance"
                  },
                  {
                    "text": "Which sources are cited?",
                    "kind": "provenance"
                  }
                ]
              }
            ]
          },
          {
            "id": "soviet",
            "name": "Soviet",
            "description": "Soviet calendar.",
            "findings": [
              {
                "id": "soviet-finding",
                "name": "Soviet",
                "description": "Soviet.",
                "questions": [
                  {
                    "text": "How did Soviet calendar experiments relate to February 30?",
                    "kind": "provenance"
                  },
                  {
                    "text": "Is the information accurate?",
                    "kind": "boundary"
                  }
                ]
              }
            ]
          }
        ]
      },
      {
        "id": "context",
        "name": "Context",
        "description": "Computing.",
        "rationale": "Regulation.",
        "layers": [
          {
            "id": "validation",
            "name": "Validation",
            "description": "Date validation.",
            "findings": [
              {
                "id": "validation-finding",
                "name": "Validation",
                "description": "Validation.",
                "questions": [
                  {
                    "text": "Why is February 30 used to test date validation?",
                    "kind": "provenance"
                  },
                  {
                    "text": "Is the information current?",
                    "kind": "boundary"
                  }
                ]
              }
            ]
          },
          {
            "id": "fiction",
            "name": "Fiction",
            "description": "Fiction and jokes.",
            "findings": [
              {
                "id": "fiction-finding",
                "name": "Fiction",
                "description": "Fiction.",
                "questions": [
                  {
                    "text": "How is February 30 used as a deliberately impossible date?",
                    "kind": "provenance"
                  },
                  {
                    "text": "Is the presentation neutral and attributed?",
                    "kind": "boundary"
                  }
                ]
              }
            ]
          }
        ]
      }
    ]
  },
  "openQuestions": [
    "How should historical exceptions be documented?",
    "How should date-validation edge cases be linked?",
    "Should the Swedish 1712 case be an instance?"
  ],
  "statistics": {
    "bundles": 4,
    "layers": 8,
    "findings": 8,
    "questions": 16
  }
}