{ "model": { "rank": 1230, "code": "thing-q19828", "model_id": "vr.tr.leap-year", "name": "leap year", "purpose": "Let an agent compute leap years correctly across calendars and handle 29 February in dates, ages and software.", "family": "Thing Registry", "category": "Cross-cutting context", "status": "research-draft", "kind": "thing", "plane": "XCT", "domain": "XCT.TME", "industry": "", "version": "", "url": "/models/thing/q19828/", "tier": 2, "score": 166, "payload": { "layer": "wikidata", "aliases": [ "century leap year", "Darian leap year", "leap year starting on Wednesday and ending on Thursday", "leap year starting on Thursday and ending on Friday", "leap year starting on Monday and ending on Tuesday", "leap year starting on Saturday and ending on Sunday", "leap year starting on Tuesday and ending on Wednesday", "leap year starting on Friday and ending on Saturday", "leap year starting on Sunday and ending on Monday" ], "aliasCount": 9, "merged": 9, "knownIn": 166, "facets": null, "markers": [], "lexicalClass": "", "senseRank": null, "alsoRegisteredAs": null, "source": { "dataset": "wikidata", "item": "Q19828", "url": "https://www.wikidata.org/wiki/Q19828", "license": "CC0 1.0" } }, "research": { "vercy": "1.0-draft", "publication": { "status": "research-draft", "adjudicationStatus": "unreviewed", "publishableCanonical": false, "generatedAt": "2026-09-11T06:57:21Z", "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": 1, "engine": "claude" }, "metaModel": { "id": "THING-Q19828", "registryId": "vr.tr.leap-year", "name": "leap year", "version": "0.2.0-wave.1", "entryKind": "thing", "family": "Thing Registry", "domain": [ "XCT.TME" ], "status": "research-draft" }, "canonicalUrl": "https://ver.cy/models/thing/q19828/", "model": { "registry_id": "vr.tr.leap-year", "name": "leap year", "purpose": "Let an agent compute leap years correctly across calendars and handle 29 February in dates, ages and software.", "definition": "A calendar year containing an extra day (or month in lunisolar calendars) to keep the calendar aligned with the astronomical year; in the Gregorian calendar, years divisible by 4 are leap years except century years not divisible by 400, and the extra day is 29 February.", "what_it_is_for": "Keeping calendars in step with the seasons.", "affordances": [ "check whether a year is a leap year", "handle 29 February in software", "compute ages and anniversaries", "convert between calendars" ], "distinguishing_features": [ "Extra intercalary day", "Gregorian rule with century exception", "Julian rule is every 4 years", "Leap seconds are a separate concept" ], "appearance": "A calendar with 366 days, including 29 February.", "visual_identification": [ "Year with 29 February", "Divisibility rule", "Leap years by starting weekday are calendar variants" ], "physical_properties": [ { "quantity": "length", "typical_range": "366", "unit": "days", "note": "Gregorian" }, { "quantity": "frequency", "typical_range": "97 in 400", "unit": "years", "note": "Gregorian" } ], "families_and_kinds": [ "Gregorian leap years", "Julian leap years", "century leap years", "lunisolar leap months", "leap years by starting weekday" ], "related_models": [ { "relation": "is a kind of", "target": "calendar year", "why": "category" }, { "relation": "is defined by", "target": "Gregorian calendar", "why": "calendar" }, { "relation": "has part", "target": "29 February", "why": "leap day" }, { "relation": "is confused with", "target": "leap second", "why": "another concept" } ], "identifiers": [], "standards_and_regulation": [ "ISO 8601 date representation", "Laws on 29 February birthdays for legal age in some countries" ], "failure_modes_and_hazards": [ "Software bugs on 29 February", "Wrong century rule", "Age calculations for leap-day births" ], "in_scope": [], "out_of_scope": [], "characteristics": [] }, "sources": [], "structure": { "bundles": [ { "id": "rule", "name": "Rule", "description": "Is it a leap year.", "rationale": "Rules differ by calendar.", "layers": [ { "id": "gregorian", "name": "Gregorian", "description": "Divisibility.", "findings": [ { "id": "gregorian-finding", "name": "Gregorian", "description": "Gregorian rule.", "questions": [ { "text": "Is this year a leap year under the Gregorian rule?", "kind": "boundary" }, { "text": "Is it a century year?", "kind": "boundary" } ] } ] }, { "id": "other", "name": "Other calendars", "description": "Julian, lunisolar.", "findings": [ { "id": "other-finding", "name": "Other", "description": "Other calendars.", "questions": [ { "text": "Under which calendar is the question asked?", "kind": "definition" }, { "text": "What rule does that calendar use?", "kind": "definition" } ] } ] } ] }, { "id": "dates", "name": "Dates", "description": "Calendar arithmetic.", "rationale": "Leap days affect arithmetic.", "layers": [ { "id": "day-count", "name": "Day count", "description": "Durations.", "findings": [ { "id": "day-count-finding", "name": "Day count", "description": "Day counting.", "questions": [ { "text": "How many days are between these dates?", "kind": "measurement" }, { "text": "Is a leap day included?", "kind": "boundary" } ] } ] }, { "id": "weekday", "name": "Weekday", "description": "Starting day.", "findings": [ { "id": "weekday-finding", "name": "Weekday", "description": "Weekday.", "questions": [ { "text": "On which weekday does the year start and end?", "kind": "measurement" }, { "text": "Which calendar pattern repeats?", "kind": "definition" } ] } ] } ] }, { "id": "software", "name": "Software", "description": "Bugs.", "rationale": "Leap days break software.", "layers": [ { "id": "handling", "name": "Handling", "description": "Libraries.", "findings": [ { "id": "handling-finding", "name": "Handling", "description": "Date handling.", "questions": [ { "text": "Does the code use a tested date library?", "kind": "boundary" }, { "text": "Is 29 February tested?", "kind": "boundary" } ] } ] }, { "id": "adding-years", "name": "Adding years", "description": "Edge cases.", "findings": [ { "id": "adding-years-finding", "name": "Adding years", "description": "Adding years.", "questions": [ { "text": "What happens when a year is added to 29 February?", "kind": "boundary" }, { "text": "Which convention applies?", "kind": "definition" } ] } ] } ] }, { "id": "people", "name": "People", "description": "Leap-day births.", "rationale": "Birthdays need rules.", "layers": [ { "id": "birthdays", "name": "Birthdays", "description": "Celebration.", "findings": [ { "id": "birthdays-finding", "name": "Birthdays", "description": "Leap-day birthdays.", "questions": [ { "text": "When does someone born on 29 February celebrate in common years?", "kind": "definition" }, { "text": "What does law say about their legal age?", "kind": "provenance" } ] } ] }, { "id": "records", "name": "Records", "description": "Forms.", "findings": [ { "id": "records-finding", "name": "Records", "description": "Records.", "questions": [ { "text": "Do forms and systems accept 29 February?", "kind": "boundary" }, { "text": "Who fixes them?", "kind": "action" } ] } ] } ] } ] }, "openQuestions": [ "Should leap years by weekday be separate entries?", "How should calendar conversions be linked?", "How should leap-day legal rules be recorded?" ], "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 leap year, record what state it is in, and decide what may be done with it.", "whatItIs": "Let an agent compute leap years correctly across calendars and handle 29 February in dates, ages and software.", "characteristics": { "substance": "abstract", "origin": "conceptual", "agency": "inert" }, "whatYouCanDoWithIt": [ "observed and measured" ], "distinguishingFeatures": [ "Names folded into this entry, which a task may need to split apart again: century leap year, Darian leap year, leap year starting on Wednesday and ending on Thursday, leap year starting on Thursday and ending on Friday, leap year starting on Monday and ending on Tuesday, leap year starting on Saturday and ending on Sunday, leap year starting on Tuesday and ending on Wednesday, leap year starting on Friday and ending on Saturday, leap year starting on Sunday and ending on Monday.", "9 finer distinctions are held as aliases rather than separate entries, because telling them apart needs a task that asks for it.", "Described in 166 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 leap year, 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": [ { "relation": "covers", "note": "Finer kinds folded into this entry because telling them apart needs a task that asks for it. Each is a model waiting to be split out when one does.", "targets": [ "century leap year", "Darian leap year", "leap year starting on Wednesday and ending on Thursday", "leap year starting on Thursday and ending on Friday", "leap year starting on Monday and ending on Tuesday", "leap year starting on Saturday and ending on Sunday", "leap year starting on Tuesday and ending on Wednesday", "leap year starting on Friday and ending on Saturday", "leap year starting on Sunday and ending on Monday" ] } ], "standing": "Described in 166 Wikipedia languages, which measures how widely it is written about rather than how important or how common it is. 9 finer distinctions are held inside this entry as names rather than as separate models.", "structure": { "bundles": [ { "id": "identity-and-classification", "name": "Identity, naming and classification", "description": "How an agent tells one leap year from another, and a leap year 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 leap year, 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 leap year, 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 leap year 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 leap year, 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 leap year, 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 leap year 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 leap year 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 leap year, 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 leap year, 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 leap year 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 leap year from the things most often confused with it.", "questions": [ { "id": "distinguishing-features-q01", "text": "What identifies and describes what distinguishes a leap year, 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 leap year, 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 leap year 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 leap year 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 leap year between them.", "questions": [ { "id": "stages-and-transitions-q01", "text": "What identifies and describes the lifecycle of a leap year, 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 leap year, 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 leap year 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 leap year, how often and by whom.", "findings": [ { "id": "observation-record", "name": "Observation record", "description": "How an observation of a leap year 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 leap year, 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 leap year, 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 leap year 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 leap year 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 leap year 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 leap year 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 leap year 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 leap year?", "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 leap year?", "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 leap year 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 leap year and how confident it is.", "questions": [ { "id": "claim-provenance-q01", "text": "What identifies and describes a claim about a leap year, 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 leap year, 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 leap year 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 leap year is retired without being erased.", "questions": [ { "id": "validity-and-supersession-q01", "text": "What identifies and describes the validity of a claim about a leap year, 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 leap year, 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 leap year 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 } } } }