Greenwich Mean Time
E3109
Greenwich Mean Time is the mean solar time at the Royal Observatory in Greenwich, London, historically used as the world’s primary reference for timekeeping and the basis for Coordinated Universal Time (UTC).
All labels observed (6)
| Label | Occurrences |
|---|---|
| Greenwich Mean Time canonical | 1,763 |
| Greenwich Mean Time (when GMT is UTC+0) | 1 |
| Greenwich Mean Time (when GMT is used as winter time) | 1 |
| International Meridian Conference of 1884 | 1 |
| Universal Time | 1 |
| Western European Time | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T24718 — 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: Greenwich Mean Time Context triple: [Cambridge, England, timeZone, Greenwich Mean Time]
-
A.
Central European Time
Central European Time is a standard time zone used by many countries in central and western Europe, typically one hour ahead of Coordinated Universal Time (UTC+1).
-
B.
Chile Standard Time
Chile Standard Time is the primary time zone used in central Chile, including regions such as Coquimbo, typically set at UTC−4 hours.
-
C.
Eastern Time Zone
The Eastern Time Zone is a standard time zone used by the eastern portion of North America, including major U.S. cities such as New York and Washington, D.C.
-
D.
Japan Standard Time
Japan Standard Time is the standard time zone used throughout Japan, set at nine hours ahead of Coordinated Universal Time (UTC+9) without daylight saving time.
-
E.
London, England
London, England is the capital and largest city of the United Kingdom, renowned as a global center for finance, culture, and politics.
- 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: Greenwich Mean Time Target entity description: Greenwich Mean Time is the mean solar time at the Royal Observatory in Greenwich, London, historically used as the world’s primary reference for timekeeping and the basis for Coordinated Universal Time (UTC).
-
A.
Central European Time
Central European Time is a standard time zone used by many countries in central and western Europe, typically one hour ahead of Coordinated Universal Time (UTC+1).
-
B.
Chile Standard Time
Chile Standard Time is the primary time zone used in central Chile, including regions such as Coquimbo, typically set at UTC−4 hours.
-
C.
Eastern Time Zone
The Eastern Time Zone is a standard time zone used by the eastern portion of North America, including major U.S. cities such as New York and Washington, D.C.
-
D.
Japan Standard Time
Japan Standard Time is the standard time zone used throughout Japan, set at nine hours ahead of Coordinated Universal Time (UTC+9) without daylight saving time.
-
E.
London, England
London, England is the capital and largest city of the United Kingdom, renowned as a global center for finance, culture, and politics.
- F. None of above. chosen
Statements (47)
| Predicate | Object |
|---|---|
| instanceOf |
civil time standard
ⓘ
time standard ⓘ time zone ⓘ |
| abbreviation | GMT ⓘ |
| associatedWith |
Prime Meridian
ⓘ
longitude 0° ⓘ |
| basisFor |
Coordinated Universal Time
ⓘ
UTC offset system ⓘ |
| category |
astronomy
ⓘ
navigation ⓘ timekeeping ⓘ |
| coordinateReference | 0 hours offset baseline ⓘ |
| coordinateSystemRole | reference for global time zones ⓘ |
| definedAs | mean solar time at the Royal Observatory, Greenwich ⓘ |
| definedRelativeTo | Earth rotation ⓘ |
| governingBody |
Maritime Greenwich
ⓘ
surface form:
Royal Observatory, Greenwich
|
| hasAlternativeName |
GMT
ⓘ
GMT ⓘ
surface form:
Greenwich time
|
| historicalRole |
basis for international civil time
ⓘ
world primary reference for timekeeping ⓘ |
| language | English term ⓘ |
| measurementType | mean solar time ⓘ |
| notSameAs | local apparent solar time at Greenwich ⓘ |
| observesDaylightSaving | false ⓘ |
| offsetRange | +00:00 year-round ⓘ |
| referenceCity |
London, England
ⓘ
surface form:
London
|
| referenceCountry | United Kingdom ⓘ |
| referenceLocation |
Maritime Greenwich
ⓘ
surface form:
Royal Observatory, Greenwich
|
| relatedStandard | International Atomic Time ⓘ |
| relatedTo |
British Summer Time
ⓘ
UT1 ⓘ Greenwich Mean Time self-linksurface differs ⓘ
surface form:
Universal Time
|
| replacedBy | Coordinated Universal Time ⓘ |
| standardizedAt | International Meridian Conference ⓘ |
| standardizedInYear | 1884 ⓘ |
| supersededInPrecisionBy | atomic time ⓘ |
| timeOffsetFromUTC | UTC+00:00 ⓘ |
| usedAs | prime meridian time standard ⓘ |
| usedAsLegalTime | true in some jurisdictions ⓘ |
| usedIn |
Iceland
ⓘ
Ireland (winter) ⓘ Portugal (mainland, winter) ⓘ United Kingdom (winter) ⓘ West Africa ⓘ
surface form:
West Africa (some countries)
some Atlantic islands ⓘ |
| usedInAviation | yes (historically, now largely UTC) ⓘ |
| usedInMaritimeNavigation | yes ⓘ |
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: Greenwich Mean Time Description of subject: Greenwich Mean Time is the mean solar time at the Royal Observatory in Greenwich, London, historically used as the world’s primary reference for timekeeping and the basis for Coordinated Universal Time (UTC).
Referenced by (1,768)
Full triples — surface form annotated when it differs from this entity's canonical label.
subject surface form:
Slough
Down District area (historical local government district)
→
locatedInTimeZone
→
Greenwich Mean Time
ⓘ
subject surface form:
Down District area
subject surface form:
Streatham
subject surface form:
Mount Pleasant, Swansea
subject surface form:
Newcastle, County Down
subject surface form:
Volta Region