{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.december-31","code":"thing-q2912","url":"https://ver.cy/models/thing/q2912/","name":"December 31","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":"December 31, day 365 (day 366 in leap years) of the year in the Gregorian calendar, with 0 days remaining; it is the last day of the year in both common and leap years. Observances on this date vary by country and tradition; it is New Year Eve in the Gregorian calendar.","purpose":"Let an agent handle December 31 as a calendar date with weekday computation, observances attributed to their traditions and sourced events.","scope":{"in":[],"out":[],"boundaries":[]},"distinguishingFeatures":["The thirty-first day of December","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 December 31 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 December 31 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 December 31, 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 December 31?","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 December 31 as day 365 or 366 and its weekday.","Describe New Year's Eve customs and when other calendars mark the new year."],"mustNot":["Present the Gregorian new year as the only new year.","Ignore time zones when stating when the year ends somewhere.","Encourage dangerous fireworks or drink-driving at New Year's Eve.","Miscount year-end deadlines in leap years."],"requiresHuman":["Fixing year-end financial or legal deadlines that fall on December 31."]},"ethics":{"considerations":["Year-end deadlines affect taxes, contracts and benefits.","Celebrations bring injuries from fireworks and road accidents."],"affectedParties":["People with year-end deadlines","Revellers and bystanders","Emergency services"]},"owners":{"steward":"Nobody: the Gregorian calendar is held in common.","roles":[],"masterSystems":[]},"relations":[{"target":"Q11187583","type":"parent","note":"registry parent class"},{"target":"December","type":"related","note":"month"},{"target":"December 30","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.december-31","Wikidata: Q2912 (https://www.wikidata.org/wiki/Q2912)","ISO 8601: --12-31 recurring date"]},"properties":{"applicability":"not-applicable","items":["day of year: 365 or 366 day - common year, leap year where different","days remaining: 0 days"]},"recognition":{"applicability":"optional","items":["Written 31 December or December 31","ISO format --12-31","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 Q2912: December 31","url":"https://www.wikidata.org/wiki/Q2912","note":"identity and sense of the item"},{"title":"Wikipedia: December 31","url":"https://en.wikipedia.org/wiki/December_31","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-q2912/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q2912/spec.json"],"providers":["Claude"],"researchStatus":"unreviewed","generatedAt":"2026-09-11T23:17:24Z","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 2026-10-06T19:51:58+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}}