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.
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 ⓘ |
Referenced by (1)
Full triples — surface form annotated when it differs from this entity's canonical label.