February 30
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.
Bundle → Layer → Finding → Questions Filled
4 bundles · 8 layers · 8 findings · 16 questions
Understand What February 30 is.
Definition
Definition.
Definition
Definition.
- What is February 30, and how does it differ from February 29, leap years, other calendars and ordinary invalid dates? definition
- Is the question about calendar history or software date validation? boundary
Cases
Historical cases.
Cases
Cases.
- What were the Swedish 1712 and Soviet calendar cases? definition
- Which entry fits calendar reform? action
Calendar Calendar rules.
February
Length of February.
February
February.
- Why does February have 28 or 29 days? provenance
- Which references are standard? provenance
Leap
Leap years.
Leap
Leap.
- How do leap years add February 29? provenance
- Which entry fits leap year? action
History History.
Sweden
Swedish 1712 case.
Sweden
Sweden.
- Why did Sweden have a 30 February in 1712? provenance
- Which sources are cited? provenance
Soviet
Soviet calendar.
Soviet
Soviet.
- How did Soviet calendar experiments relate to February 30? provenance
- Is the information accurate? boundary
Context Computing.
Validation
Date validation.
Validation
Validation.
- Why is February 30 used to test date validation? provenance
- Is the information current? boundary
Fiction
Fiction and jokes.
Fiction
Fiction.
- How is February 30 used as a deliberately impossible date? provenance
- Is the presentation neutral and attributed? boundary
Classifiers Filled
- Family
- Thing Registry
- Category
- Cross-cutting context
- Entry kind
- thing
- Plane
- XCT
- Domain
- XCT.TME
What it is Filled
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. Sweden used February 30 in 1712 as an exceptional date during a calendar transition, but Soviet calendar experiments did not establish an actual February 30. It is also used as a deliberately impossible date in computing tests and fiction, rather than a real recurring Gregorian date.
Why it exists Filled
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.
Distinguishing features Filled
- Normally invalid
- Rare historical cases
- Calendar curiosity
- Used as impossible date
What robots and AI may and may not do Filled
Must not
- Silently roll February 30 over to a March date when storing records.
- Accept February 30 in legal, medical or financial records without flagging it.
- Present the historical cases as evidence that February 30 is a normal date.
- Schedule payments, deadlines or doses on a date that does not exist.
Only with a human decision
- Correcting a record that carries February 30 as a date of birth or of a legal event.
May
- Reject February 30 as an invalid date when validating Gregorian or Julian input.
- Explain the historical cases in which a February 30 was used, citing sources.
Moral aspects Filled
- Invalid dates in official records can block people from services or benefits.
- Software that mishandles dates can cause missed obligations.
Who is affected
- People whose records carry invalid dates
- Users of scheduling systems
- Record keepers
Owners Filled
Steward
Nobody owns it; calendar standards bodies and record keepers decide how invalid dates are handled.
Links to other meta-models Filled
parent
- Q11187571 - registry parent class
related
- calendar date - in registry terms, non-standard
- February 29
- leap year
- calendar reform
What else AI and robots need to interact with it Filled
Identity and identifiers required Filled
- Vercy registry: vr.tr.february-30
- Wikidata: Q37096 (https://www.wikidata.org/wiki/Q37096)
Direct properties not applicable Not applicable
- Sweden: 30 February 1712 date - calendar realignment
- February length: 28 or 29 days note
- registry parent: 30th day of a month note
Plane XCT: no invented physical properties.
Recognition optional Filled
- 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
- Not a physical object; a date label that is normally invalid.
Capabilities and actions required Filled
- explain why it does not exist
- relay the Swedish and Soviet cases
- relay its use as an impossible date
- distinguish related concepts
Hazards and failure modes required Filled
- Treating February 30 as a normal date
- Date validation errors in software
- Confusing calendar history
Standards and interfaces required Filled
- Gregorian calendar rules
- ISO 8601 date validity
Context of use required Filled
- A non-existent or historically exceptional calendar date.
- the Swedish 1712 case
- Soviet calendar experiments
- impossible-date usage
Sources Filled
- Wikidata item Q37096: February 30 - identity and sense of the item
- Wikipedia: February 30 - general description of the item
Open questions
- How should historical exceptions be documented?
- How should date-validation edge cases be linked?
- Should the Swedish 1712 case be an instance?
Machine files
Provenance
thing registry research (pass 2) · unreviewed
Built from: models/things/publications/thing-q37096/spec.json