Daylight saving time (United States)
E503457
Daylight saving time in the United States is a seasonal clock adjustment system in which most regions advance their clocks by one hour during warmer months to extend evening daylight and then return to standard time in the colder months.
All labels observed (1)
| Label | Occurrences |
|---|---|
| Daylight saving time (United States) canonical | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T5210808 — 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: Daylight saving time (United States) Context triple: [Pyramid Lake Paiute Reservation, observes, Daylight saving time (United States)]
-
A.
Daylight Saving
"Daylight Saving" is a novel by Edward Hogan that blends psychological suspense with supernatural elements, following a troubled teenager who encounters a mysterious girl at a run-down holiday resort.
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B.
Israel Daylight Time
Israel Daylight Time is the daylight saving time observed in Israel, typically used during the summer months when clocks are set one hour ahead of standard time.
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C.
Iran Daylight Time
Iran Daylight Time is the daylight saving time observed in Iran, advancing clocks one hour ahead of the country’s standard time during the summer months.
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D.
Western European Summer Time
Western European Summer Time is the daylight saving time observed in parts of Western Europe, including countries like Portugal, typically one hour ahead of Coordinated Universal Time (UTC+1).
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E.
British Summer Time
British Summer Time is the daylight saving time observed in the United Kingdom, during which clocks are set one hour ahead of Greenwich Mean Time to extend evening daylight in the summer months.
- 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: Daylight saving time (United States) Target entity description: Daylight saving time in the United States is a seasonal clock adjustment system in which most regions advance their clocks by one hour during warmer months to extend evening daylight and then return to standard time in the colder months.
-
A.
Daylight Saving
"Daylight Saving" is a novel by Edward Hogan that blends psychological suspense with supernatural elements, following a troubled teenager who encounters a mysterious girl at a run-down holiday resort.
-
B.
Israel Daylight Time
Israel Daylight Time is the daylight saving time observed in Israel, typically used during the summer months when clocks are set one hour ahead of standard time.
-
C.
Iran Daylight Time
Iran Daylight Time is the daylight saving time observed in Iran, advancing clocks one hour ahead of the country’s standard time during the summer months.
-
D.
Western European Summer Time
Western European Summer Time is the daylight saving time observed in parts of Western Europe, including countries like Portugal, typically one hour ahead of Coordinated Universal Time (UTC+1).
-
E.
British Summer Time
British Summer Time is the daylight saving time observed in the United Kingdom, during which clocks are set one hour ahead of Greenwich Mean Time to extend evening daylight in the summer months.
- F. None of above. chosen
Statements (49)
| Predicate | Object |
|---|---|
| instanceOf |
seasonal clock adjustment system
ⓘ
timekeeping practice ⓘ |
| administeredBy | United States Department of Transportation NERFINISHED ⓘ |
| affects |
broadcast schedules
ⓘ
business hours ⓘ computer and electronic device clocks ⓘ scheduling of transportation ⓘ |
| allows | states to opt out with federal approval ⓘ |
| alsoKnownAs |
DST in the United States
NERFINISHED
ⓘ
U.S. daylight saving time NERFINISHED ⓘ |
| appliesTo | United States NERFINISHED ⓘ |
| associatedWith | time zones in the United States ⓘ |
| controversy |
debate over energy savings
ⓘ
health and sleep disruption concerns ⓘ road safety impact debates ⓘ |
| extendedBy | Energy Policy Act of 2005 NERFINISHED ⓘ |
| fallTransition | clocks revert from 2:00 a.m. to 1:00 a.m. ⓘ |
| governingLaw |
Energy Policy Act of 2005
NERFINISHED
ⓘ
Uniform Time Act of 1966 NERFINISHED ⓘ |
| historicalIntroduction | first widely used during World War I ⓘ |
| impact | shifts sunrise and sunset times on civil clocks ⓘ |
| legalBasis | federal law ⓘ |
| notObservedBy |
American Samoa
NERFINISHED
ⓘ
Hawaii NERFINISHED ⓘ Northern Mariana Islands NERFINISHED ⓘ U.S. Virgin Islands NERFINISHED ⓘ most of Arizona ⓘ territory of Guam ⓘ territory of Puerto Rico ⓘ |
| observedBy | most U.S. states ⓘ |
| partiallyObservedBy | Navajo Nation in Arizona NERFINISHED ⓘ |
| previousEndRule | last Sunday in October (before 2007) ⓘ |
| previousStartRule | first Sunday in April (before 2007) ⓘ |
| purpose |
energy conservation (historical rationale)
ⓘ
extend evening daylight during warmer months ⓘ reduce need for artificial lighting in evening ⓘ |
| reintroduced | during World War II ⓘ |
| relatedConcept |
Sunshine Protection Act proposals
NERFINISHED
ⓘ
standard time in the United States ⓘ |
| restriction | states may not unilaterally adopt permanent daylight saving time without federal law change ⓘ |
| springTransition | clocks advance from 2:00 a.m. to 3:00 a.m. ⓘ |
| standardEndRule | first Sunday in November ⓘ |
| standardizedBy | Uniform Time Act of 1966 NERFINISHED ⓘ |
| standardStartRule | second Sunday in March ⓘ |
| timeOfChange | 2:00 a.m. local time ⓘ |
| timeOffsetEffect | advances local civil time by one hour relative to standard time ⓘ |
| typicalObservationPeriod | approximately eight months each year ⓘ |
| usesTimeShift |
one hour backward in fall
ⓘ
one hour forward in spring ⓘ |
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: Daylight saving time (United States) Description of subject: Daylight saving time in the United States is a seasonal clock adjustment system in which most regions advance their clocks by one hour during warmer months to extend evening daylight and then return to standard time in the colder months.
Referenced by (1)
Full triples — surface form annotated when it differs from this entity's canonical label.