Conway’s Doomsday algorithm
E163256
Conway’s Doomsday algorithm is a mental calculation method devised by mathematician John Horton Conway for quickly determining the day of the week for any given date.
All labels observed (3)
| Label | Occurrences |
|---|---|
| Doomsday rule | 2 |
| Conway’s Doomsday algorithm canonical | 1 |
| Doomsday algorithm | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T1428686 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: Conway’s Doomsday algorithm Context triple: [John Horton Conway, notableWork, Conway’s Doomsday algorithm]
-
A.
The Calendar
"The Calendar" is a crime thriller play by Edgar Wallace that blends mystery and melodrama around horse racing and high society intrigue.
-
B.
When the Nines Roll Over
"When the Nines Roll Over" is a collection of contemporary short stories by David Benioff that explores themes of love, ambition, and disillusionment in modern urban life.
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C.
The Extra Day
The Extra Day is a 1956 British comedy film starring Sydney Chaplin, centered on the humorous misadventures that occur when a film production is unexpectedly delayed.
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D.
A Monday Date
"A Monday Date" is a classic jazz composition closely associated with pioneering American jazz pianist and bandleader Earl Hines.
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E.
Look-and-say sequence
The look-and-say sequence is a famous integer sequence where each term is generated by verbally describing the digits of the previous term, studied for its surprising combinatorial and growth properties.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: Conway’s Doomsday algorithm Target entity description: Conway’s Doomsday algorithm is a mental calculation method devised by mathematician John Horton Conway for quickly determining the day of the week for any given date.
-
A.
The Calendar
"The Calendar" is a crime thriller play by Edgar Wallace that blends mystery and melodrama around horse racing and high society intrigue.
-
B.
When the Nines Roll Over
"When the Nines Roll Over" is a collection of contemporary short stories by David Benioff that explores themes of love, ambition, and disillusionment in modern urban life.
-
C.
The Extra Day
The Extra Day is a 1956 British comedy film starring Sydney Chaplin, centered on the humorous misadventures that occur when a film production is unexpectedly delayed.
-
D.
A Monday Date
"A Monday Date" is a classic jazz composition closely associated with pioneering American jazz pianist and bandleader Earl Hines.
-
E.
Look-and-say sequence
The look-and-say sequence is a famous integer sequence where each term is generated by verbally describing the digits of the previous term, studied for its surprising combinatorial and growth properties.
- F. None of above. chosen
Statements (48)
| Predicate | Object |
|---|---|
| instanceOf |
calendar algorithm
ⓘ
day-of-week calculation method ⓘ mental calculation method ⓘ |
| advantage |
avoids large multiplications
ⓘ
suitable for mental contests and demonstrations ⓘ |
| appliesTo |
Gregorian calendar
ⓘ
linked to:
Gregorian calendar (Western churches)
Julian calendar ⓘ |
| basedOn |
Doomsday rule
ⓘ
linked to:
Conway’s Doomsday algorithm
|
| characteristic |
can be performed mentally without written notes
ⓘ
relies on memorized reference dates ⓘ uses simple integer arithmetic ⓘ |
| creator |
John Horton Conway
ⓘ
linked to:
John H. Conway
|
| developedBy |
John Horton Conway
ⓘ
linked to:
John H. Conway
|
| difficulty | requires memorization of anchor days and patterns ⓘ |
| field |
calendar calculation
ⓘ
mental arithmetic ⓘ recreational mathematics ⓘ |
| goal | enable fast mental day-of-week computation ⓘ |
| hasComplexity | constant time with respect to date size ⓘ |
| hasReferenceDate |
10/10 (10 October)
ⓘ
11/7 (7 November) ⓘ 12/12 (12 December) ⓘ 14 March (non-leap years) ⓘ 29 February (leap years) ⓘ 4/4 (4 April) ⓘ 5/9 (9 May) ⓘ 6/6 (6 June) ⓘ 7/11 (11 July) ⓘ 8/8 (8 August) ⓘ 9/5 (5 September) ⓘ last day of February ⓘ |
| hasStep |
adjust for leap years when necessary
ⓘ
compute year’s Doomsday from last two digits of year ⓘ find century anchor day ⓘ use memorized Doomsday dates within month ⓘ |
| namedAfter |
Doomsday (reference weekday for a year)
ⓘ
linked to:
Doomsday of a year
|
| notableFor | speed of mental day-of-week calculation ⓘ |
| publicationContext | popularized in expository and recreational mathematics writings ⓘ |
| relatedTo |
Tomohiko Sakamoto’s algorithm
ⓘ
Zeller’s congruence ⓘ perpetual calendar ⓘ |
| teachingUse | illustrate modular arithmetic in a practical context ⓘ |
| typicalInput | calendar date (day, month, year) ⓘ |
| typicalOutput | day of the week ⓘ |
| use | determine day of the week for a given date ⓘ |
| usesConcept |
Doomsday of a year
ⓘ
anchor day ⓘ leap year ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: Conway’s Doomsday algorithm Description of subject: Conway’s Doomsday algorithm is a mental calculation method devised by mathematician John Horton Conway for quickly determining the day of the week for any given date.
Referenced by (4)
Full triples — surface form annotated when it differs from this entity's canonical label.