February 29
Let an agent handle February 29 as a calendar date with weekday computation, observances attributed to their traditions and sourced events.
Bundle → Layer → Finding → Questions Filled
4 bundles · 8 layers · 8 findings · 16 questions
Date Calendar facts.
Weekday
Computation.
Weekday
Weekday.
- On which weekday does February 29 fall in this year? measurement
- Is it a leap year? boundary
Calendar
Julian or Gregorian.
Calendar
Calendar system.
- Is the Julian or Gregorian calendar meant? boundary
- What is the equivalent date in the other calendar? measurement
Observances Holidays.
Holiday
Public holiday.
Holiday
Holiday status.
- Is February 29 a public holiday or observance here? provenance
- Which tradition or law sets it? provenance
Attribution
Traditions.
Attribution
Attributed observances.
- Which countries or communities observe something on this date, according to them? provenance
- Is the observance attributed rather than assumed? boundary
History Past events.
Events
On this day.
Events
Historical events.
- Which notable events happened on February 29, according to reliable sources? provenance
- Are dates given in the same calendar? boundary
Anniversaries
Recurring.
Anniversaries
Anniversaries.
- Which anniversaries fall on this date this year? provenance
- Which are round numbers? measurement
Planning Scheduling.
Countdown
Days until.
Countdown
Countdown.
- How many days until the next February 29? measurement
- From which date? definition
Work
Working day.
Work
Working day.
- Is it a working day for this organisation? provenance
- Do deadlines move? boundary
Classifiers Filled
- Family
- Thing Registry
- Category
- Cross-cutting context
- Entry kind
- thing
- Plane
- XCT
- Domain
- XCT.TME
What it is Filled
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.
Why it exists Filled
Let an agent handle February 29 as a calendar date with weekday computation, observances attributed to their traditions and sourced events.
Distinguishing features Filled
- 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
What robots and AI may and may not do Filled
Must not
- 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.
Only with a human decision
- Deciding which day a legal age, contract term or benefit falls on for someone born on February 29.
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.
Moral aspects Filled
- 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.
Who is affected
- People born on February 29
- Users of scheduling and billing systems
- Record keepers
Owners Filled
Steward
Nobody: a calendar date held in common; the calendar is maintained by convention.
Links to other meta-models Filled
parent
- Q11187374 - registry parent class
related
- February - month
- February 28 - date
- calendar date - category
- ISO 8601 - notation
What else AI and robots need to interact with it Filled
Identity and identifiers required Filled
- Vercy registry: vr.tr.february-29
- Wikidata: Q2364 (https://www.wikidata.org/wiki/Q2364)
- ISO 8601: --02-29 recurring date
Direct properties not applicable Not applicable
- day of year: 60 day - common year, leap year where different
- days remaining: 306 days
Plane XCT: no invented physical properties.
Recognition optional Filled
- Written 29 February or February 29
- ISO format --02-29
- Observances vary by country and tradition
- A date on calendars.
Capabilities and actions required Filled
- compute its weekday in a given year
- check local and international observances
- find sourced historical events
- schedule events
Hazards and failure modes required Filled
- Assuming observances are universal
- Unsourced on-this-day events
- Mixing Julian and Gregorian dates
Standards and interfaces required Filled
- ISO 8601
- National public holiday laws
Context of use required Filled
- A calendar date for scheduling, holidays and anniversaries.
- the recurring calendar date
- specific dated days in given years
Sources Filled
- Wikidata item Q2364: February 29 - identity and sense of the item
- Wikipedia: February 29 - general description of the item
Open questions
- Should dated days be separate entries?
- How should observances be linked?
- How should events be sourced?
Machine files
Provenance
thing registry research (pass 2) · unreviewed
Built from: models/things/publications/thing-q2364/spec.json