{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.february-29","code":"thing-q2364","url":"https://ver.cy/models/thing/q2364/","name":"February 29","alternateNames":[],"kind":"thing","status":"published","version":"0.2.0-wave.2","language":"en","classifiers":{"family":"Thing Registry","category":"Cross-cutting context","entryKind":"thing","plane":"XCT","domain":["XCT.TME"],"industry":[],"navPath":"","tags":[],"facets":{}},"whatItIs":"February 29, day 60 (exists only in leap years) of the year in the Gregorian calendar, with 306 days remaining in leap years. February 29 is the leap day added to the Gregorian and Julian calendars in leap years to keep the calendar year aligned with the astronomical year; in the Gregorian calendar it occurs in years divisible by four, except century years not divisible by four hundred, while in the Julian calendar it occurs every four years without a century exception; people born on this date celebrate birthdays on February 28 or March 1 in common years, and observances vary by country and tradition.","purpose":"Let an agent handle February 29 as a calendar date with weekday computation, observances attributed to their traditions and sourced events.","scope":{"in":[],"out":[],"boundaries":[]},"distinguishingFeatures":["The twenty-ninth day of February","Weekday varies by year","Observances vary by place","Julian and Gregorian dates differ by 13 days in this era"],"structure":{"bundles":[{"id":"date","name":"Date","description":"Calendar facts.","layers":[{"id":"weekday","name":"Weekday","description":"Computation.","findings":[{"id":"weekday-finding","name":"Weekday","description":"Weekday.","questions":[{"text":"On which weekday does February 29 fall in this year?","kind":"measurement"},{"text":"Is it a leap year?","kind":"boundary"}]}]},{"id":"calendar","name":"Calendar","description":"Julian or Gregorian.","findings":[{"id":"calendar-finding","name":"Calendar","description":"Calendar system.","questions":[{"text":"Is the Julian or Gregorian calendar meant?","kind":"boundary"},{"text":"What is the equivalent date in the other calendar?","kind":"measurement"}]}]}]},{"id":"observances","name":"Observances","description":"Holidays.","layers":[{"id":"holiday","name":"Holiday","description":"Public holiday.","findings":[{"id":"holiday-finding","name":"Holiday","description":"Holiday status.","questions":[{"text":"Is February 29 a public holiday or observance here?","kind":"provenance"},{"text":"Which tradition or law sets it?","kind":"provenance"}]}]},{"id":"attribution","name":"Attribution","description":"Traditions.","findings":[{"id":"attribution-finding","name":"Attribution","description":"Attributed observances.","questions":[{"text":"Which countries or communities observe something on this date, according to them?","kind":"provenance"},{"text":"Is the observance attributed rather than assumed?","kind":"boundary"}]}]}]},{"id":"history","name":"History","description":"Past events.","layers":[{"id":"events","name":"Events","description":"On this day.","findings":[{"id":"events-finding","name":"Events","description":"Historical events.","questions":[{"text":"Which notable events happened on February 29, according to reliable sources?","kind":"provenance"},{"text":"Are dates given in the same calendar?","kind":"boundary"}]}]},{"id":"anniversaries","name":"Anniversaries","description":"Recurring.","findings":[{"id":"anniversaries-finding","name":"Anniversaries","description":"Anniversaries.","questions":[{"text":"Which anniversaries fall on this date this year?","kind":"provenance"},{"text":"Which are round numbers?","kind":"measurement"}]}]}]},{"id":"planning","name":"Planning","description":"Scheduling.","layers":[{"id":"countdown","name":"Countdown","description":"Days until.","findings":[{"id":"countdown-finding","name":"Countdown","description":"Countdown.","questions":[{"text":"How many days until the next February 29?","kind":"measurement"},{"text":"From which date?","kind":"definition"}]}]},{"id":"work","name":"Work","description":"Working day.","findings":[{"id":"work-finding","name":"Work","description":"Working day.","questions":[{"text":"Is it a working day for this organisation?","kind":"provenance"},{"text":"Do deadlines move?","kind":"boundary"}]}]}]}]},"agentConduct":{"may":["Compute whether a year has a February 29 under the Gregorian leap year rule.","Handle February 29 correctly in schedules, ages and anniversaries, for example in common years."],"mustNot":["Treat February 29 as an invalid date and reject records of people born on it.","Silently shift a February 29 deadline or birthday to another day without stating the rule used.","Mix Julian and Gregorian leap rules when converting historical dates.","State on-this-day events for February 29 without sources."],"requiresHuman":["Deciding which day a legal age, contract term or benefit falls on for someone born on February 29."]},"ethics":{"considerations":["Systems that mishandle the leap day can deny people services or miscalculate their legal age.","Leap day errors in software can disrupt payments, travel and safety systems."],"affectedParties":["People born on February 29","Users of scheduling and billing systems","Record keepers"]},"owners":{"steward":"Nobody: a calendar date held in common; the calendar is maintained by convention.","roles":[],"masterSystems":[]},"relations":[{"target":"Q11187374","type":"parent","note":"registry parent class"},{"target":"February","type":"related","note":"month"},{"target":"February 28","type":"related","note":"date"},{"target":"calendar date","type":"related","note":"category"},{"target":"ISO 8601","type":"related","note":"notation"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.february-29","Wikidata: Q2364 (https://www.wikidata.org/wiki/Q2364)","ISO 8601: --02-29 recurring date"]},"properties":{"applicability":"not-applicable","items":["day of year: 60 day - common year, leap year where different","days remaining: 306 days"]},"recognition":{"applicability":"optional","items":["Written 29 February or February 29","ISO format --02-29","Observances vary by country and tradition","A date on calendars."]},"capabilities":{"applicability":"required","items":["compute its weekday in a given year","check local and international observances","find sourced historical events","schedule events"]},"hazards":{"applicability":"required","items":["Assuming observances are universal","Unsourced on-this-day events","Mixing Julian and Gregorian dates"]},"interfaces":{"applicability":"required","items":["ISO 8601","National public holiday laws"]},"context":{"applicability":"required","items":["A calendar date for scheduling, holidays and anniversaries.","the recurring calendar date","specific dated days in given years"]}},"sources":[{"title":"Wikidata item Q2364: February 29","url":"https://www.wikidata.org/wiki/Q2364","note":"identity and sense of the item"},{"title":"Wikipedia: February 29","url":"https://en.wikipedia.org/wiki/February_29","note":"general description of the item"}],"openQuestions":["Should dated days be separate entries?","How should observances be linked?","How should events be sourced?"],"resources":{"spec":"/models/things/publications/thing-q2364/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q2364/spec.json"],"providers":["Claude"],"researchStatus":"unreviewed","generatedAt":"2026-09-12T05:08:46Z","builder":"tools/build_cards.py@1.0.0"},"completeness":{"sections":{"classifiers":"filled","whatItIs":"filled","purpose":"filled","distinguishingFeatures":"filled","structure":"filled","agentConduct":"filled","ethics":"filled","owners":"filled","relations":"filled","interaction.identity":"filled","interaction.properties":"not-applicable","interaction.recognition":"filled","interaction.capabilities":"filled","interaction.hazards":"filled","interaction.interfaces":"filled","interaction.context":"filled","sources":"filled"},"notes":{"_gate":"Published through the thing publication gate 1.0 on 2026-10-07T10:10:29+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass","interaction.properties":"Plane XCT: no invented physical properties."},"score":1.0}}