{ "model": { "rank": 2319, "code": "thing-q37096", "model_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.", "family": "Thing Registry", "category": "Cross-cutting context", "status": "research-draft", "kind": "thing", "plane": "XCT", "domain": "XCT.TME", "industry": "", "version": "", "url": "/models/thing/q37096/", "tier": 2, "score": 109, "payload": { "layer": "wikidata", "aliases": [], "aliasCount": 0, "merged": 0, "knownIn": 109, "facets": null, "markers": [], "lexicalClass": "", "senseRank": null, "alsoRegisteredAs": null, "source": { "dataset": "wikidata", "item": "Q37096", "url": "https://www.wikidata.org/wiki/Q37096", "license": "CC0 1.0" } }, "research": { "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" }, "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; it has appeared in a few historical and special cases, such as Sweden in 1712, when a botched calendar transition added a February 30 to realign its calendar, and in the Soviet revolutionary calendar experiments, and it is used as a deliberately impossible date in computing tests and fiction. It is a curiosity of calendar history rather than a real recurring 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": [] }, "sources": [], "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 } }, "draft": { "generator": "vr.draft.v3", "status": "draft-generated", "researched": false, "archetype": "abstract concept", "method": "Written from the archetype playbook - what this kind of thing needs beyond identity and provenance - and from the structure that recurred across 6,333 models already researched by two engines. Applied to this entry by rule. No source was read for this thing and no claim here is researched. This entry carries no facets of its own, so they were inferred from its domain - a guess about a whole domain applied to one thing.", "facetsInferred": true, "nextPass": "A researcher replaces this draft with a sourced specification. Treat every sentence below as a proposal to argue with.", "purpose": "Give an agent a durable, checkable way to recognise a February 30, record what state it is in, and decide what may be done with it.", "whatItIs": "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.", "characteristics": { "substance": "abstract", "origin": "conceptual", "agency": "inert" }, "whatYouCanDoWithIt": [ "observed and measured" ], "distinguishingFeatures": [ "Described in 109 Wikipedia languages, which is a measure of how widely the thing is known, not of how important it is." ], "openQuestionsForResearch": [ "Which of the bundles below does a real task actually need, and which are ceremony?", "What does this thing have that the facets do not capture at all?", "Which neighbouring kind is most often confused with a February 30, and on what evidence are they told apart?" ], "whatItIsMadeOf": "an abstraction with no physical instance", "physicalCharacter": [ "Does nothing on its own; everything it does, something else did to it.", "These come from the domain this entry sits in rather than from the entry itself, so treat them as a first guess about the whole domain applied to one thing." ], "whatCanBeDoneWithIt": [ "observe it, measure it, record its state" ], "howItIsRecognised": [ "Nothing to see. What is recognised is an instance of it, and which instances count is exactly what is argued about." ], "relatedModels": [], "standing": "Described in 109 Wikipedia languages, which measures how widely it is written about rather than how important or how common it is.", "structure": { "bundles": [ { "id": "identity-and-classification", "name": "Identity, naming and classification", "description": "How an agent tells one February 30 from another, and a February 30 from things that resemble it.", "rationale": "Recognition comes before every other claim. Without stable identity nothing else in the model can be trusted to be about the same thing twice.", "layers": [ { "id": "naming-and-identifiers", "name": "Names and identifiers", "description": "The names this thing goes by and the identifiers that survive translation and time.", "findings": [ { "id": "preferred-name-and-aliases", "name": "Preferred name, aliases and local names", "description": "Which name to use, which names mean the same thing, and which merely sound similar.", "questions": [ { "id": "preferred-name-and-aliases-q01", "text": "What identifies and describes the name of a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "preferred-name-and-aliases-q02", "text": "Who or what asserted this about the name of a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "preferred-name-and-aliases-q03", "text": "What may an agent decide or do once the name of a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] }, { "id": "stable-identifiers", "name": "Stable identifiers and external keys", "description": "Identifiers that keep pointing at this kind of thing across systems and languages.", "questions": [ { "id": "stable-identifiers-q01", "text": "What identifies and describes an identifier for a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "stable-identifiers-q02", "text": "Who or what asserted this about an identifier for a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "stable-identifiers-q03", "text": "What may an agent decide or do once an identifier for a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] } ] }, { "id": "classification-and-granularity", "name": "Classification and granularity", "description": "Where a February 30 sits among kinds, and how finely a task needs to cut it.", "findings": [ { "id": "kind-and-parents", "name": "Kind, parents and neighbouring kinds", "description": "The classes this thing belongs to and the ones it is next to.", "questions": [ { "id": "kind-and-parents-q01", "text": "What identifies and describes the kind of a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "kind-and-parents-q02", "text": "Who or what asserted this about the kind of a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "kind-and-parents-q03", "text": "What may an agent decide or do once the kind of a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] }, { "id": "distinguishing-features", "name": "Distinguishing features", "description": "What separates a February 30 from the things most often confused with it.", "questions": [ { "id": "distinguishing-features-q01", "text": "What identifies and describes what distinguishes a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "distinguishing-features-q02", "text": "Who or what asserted this about what distinguishes a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "distinguishing-features-q03", "text": "What may an agent decide or do once what distinguishes a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] } ] } ] }, { "id": "state-and-lifecycle", "name": "State and lifecycle", "description": "The states a February 30 passes through and the events that move it between them.", "rationale": "Most decisions about a thing depend on what state it is in now, which is a claim with a time on it, not a property.", "layers": [ { "id": "lifecycle-stages", "name": "Lifecycle stages", "description": "From coming into existence to ceasing to be one of these.", "findings": [ { "id": "stages-and-transitions", "name": "Stages and transitions", "description": "The stages worth naming and what moves a February 30 between them.", "questions": [ { "id": "stages-and-transitions-q01", "text": "What identifies and describes the lifecycle of a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "stages-and-transitions-q02", "text": "Who or what asserted this about the lifecycle of a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "stages-and-transitions-q03", "text": "What may an agent decide or do once the lifecycle of a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] } ] }, { "id": "observations-and-status", "name": "Observations and current status", "description": "What is observed about a February 30, how often and by whom.", "findings": [ { "id": "observation-record", "name": "Observation record", "description": "How an observation of a February 30 is recorded so that it can be superseded rather than overwritten.", "questions": [ { "id": "observation-record-q01", "text": "What identifies and describes an observation of a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "observation-record-q02", "text": "Who or what asserted this about an observation of a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "observation-record-q03", "text": "What may an agent decide or do once an observation of a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] } ] } ] }, { "id": "definitions-in-contest", "name": "Definitions and who holds them", "description": "What February 30 is taken to mean, and by whom.", "rationale": "When a field disagrees about a concept, the disagreement is the content. A model that picks one definition silently destroys the information.", "layers": [ { "id": "competing-definitions", "name": "Competing definitions", "description": "The main readings and the traditions behind them.", "findings": [ { "id": "definition-map", "name": "Definitions and their holders", "description": "Each definition with the school or body that holds it.", "questions": [ { "id": "definition-map-q01", "text": "Which definitions of February 30 are in use, and which tradition or body holds each?", "kind": "definition" }, { "id": "definition-map-q02", "text": "What turns on the difference between them in practice?", "kind": "boundary" } ] } ] }, { "id": "operationalisation", "name": "Operationalisation", "description": "How it is measured or applied when it has to be.", "findings": [ { "id": "operational-record", "name": "Measures and proxies", "description": "Instruments and indicators used to stand in for it.", "questions": [ { "id": "operational-record-q01", "text": "How is February 30 operationalised or measured in practice, and by what instrument?", "kind": "measurement" }, { "id": "operational-record-q02", "text": "What does that operationalisation leave out, and when does that matter?", "kind": "boundary" } ] } ] } ] }, { "id": "instances-and-use", "name": "Instances, use and consequence", "description": "What counts as an instance of February 30 and what follows from calling something that.", "rationale": "Applying a concept is an act with consequences, so a model must say what the label licenses and what it does not.", "layers": [ { "id": "instances", "name": "What counts as an instance", "description": "Clear cases, borderline cases and non-cases.", "findings": [ { "id": "instance-tests", "name": "Tests for an instance", "description": "What would settle whether something falls under it.", "questions": [ { "id": "instance-tests-q01", "text": "What would settle whether something is an instance of February 30?", "kind": "boundary" }, { "id": "instance-tests-q02", "text": "Which borderline cases are argued about, and on what grounds?", "kind": "definition" } ] } ] }, { "id": "consequence", "name": "Consequence of application", "description": "Rights, duties or decisions that follow from the label.", "findings": [ { "id": "consequence-record", "name": "What the label licenses", "description": "What an agent may do once something is classified this way.", "questions": [ { "id": "consequence-record-q01", "text": "What follows practically once something is treated as February 30?", "kind": "action" }, { "id": "consequence-record-q02", "text": "What must an agent not infer from the label alone?", "kind": "action" } ] } ] } ] }, { "id": "provenance-and-evidence", "name": "Provenance, evidence and time", "description": "Where every claim about a February 30 came from and when it held.", "rationale": "A claim without a source and a time cannot be superseded, only overwritten, and an agent that overwrites loses the ability to explain itself.", "layers": [ { "id": "source-and-authority", "name": "Source and authority", "description": "Who said it, on what evidence, and how strongly.", "findings": [ { "id": "claim-provenance", "name": "Claim provenance and confidence", "description": "The authority behind each claim about a February 30 and how confident it is.", "questions": [ { "id": "claim-provenance-q01", "text": "What identifies and describes a claim about a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "claim-provenance-q02", "text": "Who or what asserted this about a claim about a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "claim-provenance-q03", "text": "What may an agent decide or do once a claim about a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] } ] }, { "id": "time-and-versions", "name": "Time, versions and supersession", "description": "When a claim was true, when it was learnt, and what replaced it.", "findings": [ { "id": "validity-and-supersession", "name": "Validity period and supersession", "description": "How an old claim about a February 30 is retired without being erased.", "questions": [ { "id": "validity-and-supersession-q01", "text": "What identifies and describes the validity of a claim about a February 30, and in what units or vocabulary?", "kind": "definition", "answer_data": [ "identifiers", "types and classes", "values with units", "explicit unknowns" ] }, { "id": "validity-and-supersession-q02", "text": "Who or what asserted this about the validity of a claim about a February 30, by which method, and when was it true?", "kind": "provenance", "answer_data": [ "authority", "method", "evidence", "event time", "knowledge time" ] }, { "id": "validity-and-supersession-q03", "text": "What may an agent decide or do once the validity of a claim about a February 30 is known, and what must it refuse?", "kind": "action", "answer_data": [ "permitted actions", "preconditions", "refusals", "escalation" ] } ] } ] } ] } ] }, "statistics": { "bundles": 5, "layers": 10, "findings": 12, "questions": 32 } } } }