Contents

• Introduction
• The Development of Standard Time and Daylight Saving Time
• The Calder Act or the Standard Time Act of 1918
• The Uniform Time Act of 1966
• Other Changes to Standard Time and DST
• Temporary Year-Round DST
• Adjustments to the Length of DST Observance
• Other Changes
• Potential Effects of DST
• Traffic and Pedestrian Safety
• Energy Savings
• Health
• Department of Transportation's Regulation of Time Zones
• Selected State Actions to Change DST Observance
• Selected International DST Policies
• Potential Issues for Congress

Summary

Daylight saving time (DST) is a period of the year between spring and fall when clocks in most parts of the United States are set one hour ahead of standard time. DST begins on the second Sunday in March and ends on the first Sunday in November. The beginning and ending dates are set in statute. Congressional interest in the potential benefits and costs of DST has resulted in changes to DST observance (including periods of no federal DST observance) since it was first adopted in the United States in 1918.

The United States established standard time zones and DST through the Calder Act, also known as the Standard Time Act of 1918. The issue of consistency in time observance was further clarified by the Uniform Time Act of 1966. These laws as amended allow a state to exempt itself—or parts of the state that lie within a different time zone—from DST observance. As amended, these laws also authorize the Department of Transportation (DOT) to regulate standard time zone boundaries and DST. Only Congress can change the DST observance period, which was changed most recently in the Energy Policy Act of 2005 (EPACT 2005; P.L. 109-58).

Congress has required several agencies to study the effects of changes in DST observance. In 1974, DOT reported that the potential benefits of extending DST observance year-round to energy conservation, traffic safety, and reductions in violent crime were minimal. In 2008, the Department of Energy assessed the effects to national energy consumption of extending DST as changed in EPACT 2005 and found a reduction in total primary energy consumption of 0.02%. Other studies have examined potential health effects associated with the spring and fall transition to DST and found a cumulative effect of sleep loss and increased relative risk in specific subgroups for diagnosis of acute myocardial infarction (heart attacks), immune-related disorders, and mental and behavioral disorders.

Though the authority to change the DST observance period rests solely with Congress, since 2015, 47 states have proposed legislation to change their observance of DST. These efforts include proposals to exempt a state from DST observance, which is allowable under existing law, and proposals that would effectively establish permanent DST, which could take effect only if Congress were to amend the Uniform Time Act of 1966. Most of the proposals have not passed. Nineteen states have enacted legislation that would implement permanent DST if and when such action is allowed by Congress: Alabama, Colorado, Delaware, Florida, Georgia, Idaho, Louisiana, Maine, Minnesota, Mississippi, Montana, Oklahoma, Oregon, South Carolina, Tennessee, Texas, Utah, Washington, and Wyoming.

Congress may consider whether to make additional changes to DST observance or standard time. Several bills introduced in the 119^th Congress would make such changes. The Sunshine Protection Act of 2025 (H.R. 139 and S. 29) would effectively implement year-round DST for most states and areas. On July 14, 2026, the House passed H.R. 139. The Daylight Act (H.R. 300) would provide flexibility to the current DST observance period by adding an option for year-long DST observance. The Daylight Act of 2026 (H.R. 7378) would repeal DST and advance standard time by 30 minutes. The Sunshine for Our Kids Act of 2026 (H.R. 9638) would repeal DST, effectively implementing year-round standard time.

Congress could also consider the potential implications of maintaining DST year-round, of maintaining standard time year-round, or of maintaining the current status quo of alternating between the two. For example, on April 10, 2025, the Senate Committee on Commerce, Science, and Transportation held a hearing to consider issues related to the nation's observance of time. Congress could consider further study on the benefits and costs of the different options. Also in the 119^th Congress, H.R. 9237 and S. 4744 would direct the Secretary of Veterans Affairs to ensure that the Veterans Health Administration has call centers in certain time zones, with an exception for any location generally "that does not follow daylight saving time," among other provisions. Federal program eligibility requirements contingent upon DST observance could introduce additional complexities to the issue of DST.

Introduction

Daylight saving time (DST) is a period of the year between spring and fall when clocks in most parts of the United States are set one hour ahead of standard time. The beginning and ending dates and times—the second Sunday in March at two o'clock ante meridian (2:00 a.m.) and the first Sunday in November at 2:00 a.m.—are set in statute.¹ Congressional interest in the potential benefits and costs of DST has resulted in changes to DST observance since it was first adopted in the United States.

DST advances the observance of time by one hour in relation to solar time.² For example, if noon is the time of day when the sun appears to have reached its highest point in the sky according to solar time, during DST, the sun would be at its highest point in the sky at 1:00 p.m. As a result, during DST, individuals who follow clock-based schedules conduct their daily routines one hour earlier according to the apparent motion of the sun. By shifting clock-based schedules at scale, proponents hope to make use of sunlight in many locations during more of the hours when people are typically active.

Congress may consider whether to make additional changes to DST observance or standard time. Congress may also consider whether additional examination of potential benefits and costs of DST observance would be informative. In the 119^th Congress, several bills have been introduced, and the Senate Committee on Commerce, Science, and Transportation held a hearing to examine the issue.³ This report presents a selected history of DST in the United States and includes a summary of potential effects, selected state actions and international actions related to DST or standard time, and federal legislation that has been introduced related to DST in the 119^th Congress.

The Development of Standard Time and Daylight Saving Time

The development of railroads led to the creation of a standard time in the United States. To reduce the confusion resulting from locally established "sun times" (local solar times) at railroad terminals, U.S. and Canadian railroads adopted four standard time zones in 1883.⁴ The four established time zones were the Eastern, Central, Mountain, and Pacific. Adoption of time zones at the local level was influenced by the time zones adopted by the railroads.⁵

The Calder Act or the Standard Time Act of 1918

In 1918, Congress passed an act to provide standard time for the United States (also known as the Calder Act and the Standard Time Act of 1918).⁶ The Calder Act established five standard time zones for the continental United States and Alaska (which was a territory at the time)—effectively what are referred to as the Eastern, Central, Mountain, Pacific, and Alaska standard time zones. The Calder Act made no provisions for standard time for Hawaii (which was a territory at the time), Puerto Rico, or any other U.S. territory or possession. It authorized the Interstate Commerce Commission (ICC) to fix the time zone boundaries within the United States and to change them as necessary. The act also set a summer DST to begin on the last Sunday of March and conclude on the last Sunday in October. The adoption of DST in the United States was preceded by adoption of DST in Europe during World War I.⁷ After World War I, Congress abolished summer DST at the federal level, although it remained a local option, with some states continuing to observe it.⁸ With a few exceptions, this patchwork of local DST observance continued into the 1960s when the ICC recommended that Congress reexamine the issue.

The Uniform Time Act of 1966

In 1961, the ICC recommended that Congress reexamine "the entire field of standard time."⁹ According to the ICC, "the growing inconvenience, confusion, and sometimes danger, resulting from this time situation would seem too great a price to pay merely to preserve the right of local option in matters of standard time."¹⁰ The reexamination resulted in the Uniform Time Act of 1966 (P.L. 89-387).¹¹ The act mandated standard time within the established time zones and specified the observance period for DST: Clocks would be advanced one hour beginning at 2:00 a.m. on the last Sunday in April and turned back one hour at 2:00 a.m. on the last Sunday in October. States were allowed to exempt themselves from DST as long as the entire state did so.¹² If a state chose to observe DST, the time changes were required to begin and end on the established dates. The ICC was authorized with implementing the act until the authorities were transferred to the Department of Transportation (DOT), which occurred in October 1966 through the Department of Transportation Act (P.L. 89-670).¹³

In 1972, the Uniform Time Act was amended (P.L. 92-267) to also allow states that were split between time zones¹⁴ to exempt from DST that part of the state lying within a different time zone.

Most states observe DST. The following states and territories do not observe DST: American Samoa, most of Arizona, Guam, Hawaii, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands.¹⁵

Other Changes to Standard Time and DST

Temporary Year-Round DST

Year-round DST has been implemented twice on a temporary basis in the United States. In 1942, Congress enacted a law to institute year-round DST, which became known as "War Time."¹⁶ The law advanced the standard time for each time zone by one hour to be in effect until six months after the war ended or earlier if Congress required in a subsequent concurrent resolution. Congress opted to keep War Time throughout World War II; Congress passed a subsequent law ending War Time on the last Sunday in September 1945.¹⁷ After September 1945, the United States observed standard time without nationwide changes to time until enactment of the Uniform Time Act of 1966.¹⁸

The second time Congress required year-round DST was in the 1970s. During the 1973 oil embargo by the Organization of Arab Petroleum Exporting Countries (OAPEC), Congress enacted the Emergency Daylight Saving Time Energy Conservation Act of 1973 (P.L. 93-182), which established a trial period of year-round DST, from January 6, 1974, to April 27, 1975.¹⁹ The act, among other provisions, directed the Secretary of Transportation to submit interim and final reports to Congress on the operation and effects of the act and to include recommendations for legislation or other action. During the trial period, an interim report to Congress by DOT recommended amending the trial period to include four months of standard time.²⁰ In response, Congress amended the act in October 1974 (P.L. 93-434), requiring a return to standard time for a four-month period beginning October 27, 1974, and ending February 23, 1975, when DST resumed.²¹ When the trial period ended on April 27, 1975, the country resumed the seasonal observance of DST (with the aforementioned exceptions).

Adjustments to the Length of DST Observance

Congress has made additional changes to the Uniform Time Act that lengthened the DST observance period. In 1986, Congress enacted P.L. 99-359, which changed the beginning of DST from the last Sunday in April to the first Sunday in April. In 2005, Section 110 of the Energy Policy Act of 2005 (P.L. 109-58) amended the Uniform Time Act by further lengthening DST to begin the second Sunday in March and end the first Sunday in November (it had previously ended the last Sunday in October); this DST period remains in effect today. The act required the Secretary of the Department of Energy (DOE) to report to Congress on the impact of extended DST on energy consumption in the United States (see section on "Energy Savings").²²

Other Changes

Other legislative changes addressed time zones. P.L. 106-564 amended the Calder Act to create Chamorro standard time, which includes Guam and the Commonwealth of the Northern Mariana Islands.²³ It also amended the Uniform Time Act of 1966 to include Guam and the Northern Mariana Islands in the definition of "State."²⁴ In 2007, Congress and the President enacted the America COMPETES Act (P.L. 110-69).²⁵ Section 3013 of this act made changes to the Uniform Time Act regarding standard time in the United States, including a change to Idaho's time zone.

For a timeline of selected federal legislative actions, see Table A-1.

Potential Effects of DST

Support and opposition to changes in DST observance often focus on its potential effects, including potential effects to economic development; outdoor recreation; traffic and pedestrian safety, including school commutes; energy savings; and human health. Those in favor of extending DST observance reportedly argue that the extended daylight in the evening can promote economic activity and outdoor recreation, while those against it argue that losing an hour of daylight in the morning could affect morning maintenance operations and recreation for some outdoor recreation sites. One example is the golf industry, which does not have a uniform stance and recognizes potential impacts to both morning and evening operations.²⁶

A number of studies have assessed DST's effects on safety, energy savings, and health. Proponents of DST have suggested that shifting clock-based schedules at scale could potentially reduce energy consumption for some energy loads (e.g., artificial lighting) by making use of sunlight during more of the hours when people are typically active; however, this change in schedules can affect the amount of sunlight during morning or evening commutes, which could affect traffic and pedestrian safety. In addition, changing clocks forward or backward could disrupt sleep patterns and have other health effects. This section discusses a selection of these issues—including studies mandated by Congress. This is not a comprehensive review of the literature.

Congress has required agencies to evaluate the effects of DST. For example, DOT provided an interim evaluation in 1974 and final report in 1975 on the operation and effects of extending DST.²⁷ The interim report's findings were inconclusive, stating that the observed effects were "so small that they could not in general be reliably separated from effects of other changes occurring at the time."²⁸ The report concluded that, "there is no unambiguous direct evidence that [the measurable effects of year-round daylight saving time] were either beneficial or harmful."²⁹ The final report noted that the study's findings "do not provide conclusive support for recommending permanent changes in the Uniform Time Act of 1966," but rather concluded that

[m]odest overall benefits might be realized by a shift from the historic 6-month DST system (May through October) to an 8-month DST system (March through October), in the areas of conservation, overall traffic safety, and reduced violent crime. The potential benefits, however, are small and difficult to isolate completely from the larger effects of seasonal patterns and changes in energy availability and prices.³⁰

After DOT submitted its final report to Congress in 1975, Congress directed the National Bureau of Standards (NBS)³¹ to conduct a technical evaluation of selected aspects of the DOT study and to deliver a report to Congress. In its report, NBS found no significant energy savings or differences in motor vehicle fatalities.³²

Traffic and Pedestrian Safety

Among other potential effects, the NBS study evaluated school-age children traffic fatalities to determine the effect of DST on the safety of school-age children. NBS found statistically significant evidence of increased fatalities among school-age children in the mornings during the four-month period of DST observance in 1974 (from January to April) as compared with the same period (non-DST) in 1973; however, NBS warned that "this increase cannot be simply interpreted as a 'DST effect,' in view of the many other factors that influence traffic fatalities.³³

Since the DOT and NBS analyses, many studies have examined the potential effects of DST on traffic and pedestrian safety. Many factors affect pedestrian safety, including physical and environmental conditions, traffic conditions, and socioeconomic characteristics of the location.³⁴ For example, in the United States, the majority of traffic-related pedestrian fatalities occur in urban areas (84% in 2023) and typically occur at locations other than at road intersections (for both urban and rural areas).³⁵ More pedestrian fatalities in the United States occur in the dark (77% in 2023) than during other light conditions (i.e., dawn, daylight, and dusk).³⁶ A 2025 study on DST and fatal crashes found that "light condition and the type of road user are key determinants of the impact of time changes on fatal crashes."³⁷ The study found that pedestrian and bicyclist fatal crashes were more strongly associated with ambient light conditions than motor-vehicle-occupant fatal crashes.³⁸ Switching between DST and standard time could have implications during morning or evening commutes; however, lighting conditions are only one of many factors that contribute to traffic crashes involving pedestrians.

A number of studies have assessed potential short- and long-term effects on traffic and pedestrian safety and have reached difference conclusions.³⁹ Some studies have found that the short-term effect of DST on crashes is not statistically significant.⁴⁰ One review of the scientific literature noted that while findings on the short-term effects of DST were inconsistent, the long-term effects of DST suggest a positive effect (i.e., DST is associated with a reduction in collisions, injuries, and fatalities).⁴¹ However, the long-term results "may be attributable to factors other than light," such as traffic flow or weather conditions.⁴² Another study suggested that "it appears more likely that the beneficial long-term effects reported in prior studies are attributable to seasonal changes rather than DST per se."⁴³ The study also found that the spring DST transition increased fatal traffic crash risk by 6% in the United States, with the highest accident risk occurring in the morning; according to the authors, the increased risk was likely attributable to increased driver sleepiness, with lighting conditions playing a contributing role.⁴⁴ No effects on traffic crashes were observed for the autumn transition to standard time—which, according to the authors, supports the hypothesis that circadian misalignment and sleep deprivation are factors for traffic crash risk.⁴⁵ This study also observed the traffic crash risk before and after the Energy Policy Act of 2005 (P.L. 109-58) changed the length of observance of DST and found that "increases in [motor vehicle accident (MVA)] risk were indeed directly linked to the DST transition."⁴⁶ These findings, according to the authors, "support the theory that abolishing time changes completely, would improve public health and reduce geographical health disparities, as observed in our time zone analysis."⁴⁷

Responding to the study's findings, another researcher noted that "the amendments in the Uniform Time Act made by the Energy Policy Act [of 2005] doubled the increase of fatal morning MVA attributed to the spring transition" and suggested that the analysis "calls for discontinuing the provisions of the Energy Policy Act relative to transition dates."⁴⁸ In response, the original authors replied that

[a]lthough our data support the conclusion that we should stop switching between [standard time (ST)] and DST, it does not contribute to the question regarding if DST or ST is to be preferred. However, generally speaking, there is evidence that it would be better for sleep, the body clock, and overall health to have more morning light and less evening light. These arguments support permanent ST.⁴⁹

Energy Savings

In addition to the studies by DOT and NBS that included considerations of energy savings, as part of the Energy Policy Act of 2005 (P.L. 109-58), Congress directed DOE to evaluate energy savings resulting from extending DST. In 2008, DOE submitted a report to Congress on the effects of the extended DST on U.S. energy consumption.⁵⁰ DOE found that the total electricity savings associated with the extended DST corresponded to a 0.03% decrease in electricity consumption in 2007. This represents approximately 0.02% of total U.S. energy consumption in 2007.⁵¹ Regionally, areas in the northern United States exhibited larger electricity savings than areas in the southern United States. DOE reported that there was insufficient statistical evidence to indicate whether extended DST "had any measurable impact on motor gasoline consumption for passenger vehicles or traffic volume in 2007."⁵²

Other studies also evaluated potential energy savings associated with DST, including the role that geography may play. One literature review reported a reduction in national electricity use of approximately 0.5% and noted that "existing knowledge about how DST affects electricity use is limited, incomplete, or contradictory."⁵³ Another review concluded that "applied studies have produced limited, incomplete, and, in some cases, contradictory results, mainly because they often do not fully consider economic, geographical, climatological, and behavioral factors."⁵⁴ At least one empirical study based in Indiana found that DST increased electricity demand.⁵⁵ Havranek et al. (2018) conducted a literature review and found that "electricity savings are larger for countries [or areas] farther away from the equator, while subtropical regions consume more electricity because of DST."⁵⁶ A study of energy consumption in Turkey before and after the repeal of the observance of DST in 2016 did not observe a decrease in energy consumption due to DST; the authors claim that the findings should apply to the United States and other countries whose latitudes include land between 42.0 degrees north and south of the equator.⁵⁷ A 2023 study analyzing the cooling and heating demand of office buildings in 15 cities in the United States found that DST reduces overall thermal energy use for those office buildings, including under some potential climate change projections.⁵⁸ The study did not evaluate the potential tradeoffs in shifting energy loads between office buildings and residential buildings or in shifting the energy source to meet the thermal demand (e.g., electricity or fuel).⁵⁹

Health

Studies have examined potential health effects related to the semiannual changing of the clock per DST.⁶⁰ At issue is the effect of desynchronization of local observed time, local sun time, and the body's time, which is largely set by light and darkness and affects physiological functions.⁶¹ Some note that desynchronizations can occur when subjects spend significant time indoors, rely heavily on artificial light, live at an extreme eastern or western edge of a time zone, and/or live in a location that observes DST (where the effective time zone during DST would be one time zone further east).⁶² Studies suggest that the effect of DST on sleep can be cumulative and is additive with nighttime light exposure (e.g., from smartphones).⁶³ Subsequent changes in mood, cognition, and stress reactivity may further impair sleep quality, which may be particularly relevant in individuals with preexisting psychiatric conditions and chronic mental illness.⁶⁴

Several studies have examined the incidence of acute health effects associated with transitions to and from DST. Some of the studies found evidence that spring shifts to DST are associated with increased incidence of acute myocardial infarction (AMI, or heart attack).⁶⁵ One study found evidence that both spring and fall transitions are associated with increased incidence of AMI.⁶⁶ Other studies did not find a relation between the transition to or from DST and AMI.⁶⁷ One study found no significant changes in AMI risk during the first three days or one week after the transition to and from DST but did conclude that "specific subgroups such as men and persons with a history of AMI or prior treatment with angiotensin-converting-enzyme (ACE) inhibitors may have a higher risk for AMI during DST."⁶⁸ Another study found increased risk of out-of-hospital cardiac arrest following the spring DST transition and decreased risk of out-of-hospital cardiac arrest following the fall DST transition.⁶⁹ Other acute effects may include increased risk of hospitalization for ischemic stroke.⁷⁰ One study that relied upon electronic health records found that the exposure to the transition to or from DST was associated with "modest" increased diagnosis rates for cardiovascular diseases, injuries, mental and behavioral disorders, and immune-related diseases, and decreased diagnosis rates for some infectious and immune diseases, immediately after the spring DST transition.⁷¹

Fewer studies have examined potential chronic effects of DST, in part because seasonal effects can potentially confound comparisons of DST and standard time. Chronic effects of DST may be small on an individual level but across populations could have larger effects.⁷² Some studies have examined the relationship between relative position within a time zone and cancer prevalence with different conclusions. One study analyzed cancer diagnoses in a subpopulation (to reduce confounding factors) within 607 counties of the United States and found that residents in the western regions of time zones were at increased risk for overall cancer and for many specific cancers, which is consistent with a hypothesis of circadian disruption.⁷³ Another study, done in response to the previous study, analyzed a larger set of cancer diagnoses from 2,853 counties in 48 states of the United States—adjusting for race, educational attainment, access to health care, and other factors—and found that "there is no discernible cancer-related reason to favor one time system over the other."⁷⁴ The study found that

[c]ancer rate differences lack statistical significance within time zones and near borders for total cancer and most individual cancers. Exceptions included breast, prostate, and liver and bile duct cancers, which exhibited significant relationships with relative position at the 95% significance level. Breast and liver and bile duct cancers saw decreases, while prostate cancer incidence increased from west to east within time zones.⁷⁵

The study concluded that "relative position does not have a significant impact on cancer incidence, hence cancer development in general."⁷⁶ According to one review of the literature, "current evidence suggests that the health effects of DST are neither uniformly harmful nor uniformly beneficial."⁷⁷

Several scientific and medical organizations support permanent standard time. The Society for Research on Biological Rhythms Executive Board approved a position paper that supports "removing DST changes or removing permanent DST and having governing organizations choose permanent Standard Time for the health and safety of their citizens."⁷⁸ In 2020, the American Academy of Sleep Medicine (AASM) recommended ceasing the seasonal changing of clocks in favor of a year-round fixed time, stating that "current evidence best supports the adoption of year-round standard time, which aligns best with human circadian biology and provides distinct benefits for public health and safety."⁷⁹ In 2024, an updated statement by AASM recommended eliminating seasonal time changes in favor of permanent standard time, "which aligns best with human circadian biology."⁸⁰

Department of Transportation's Regulation of Time Zones

Although states may exempt themselves, in whole or in part, from DST, they cannot independently change time zones or alter the length of DST (i.e., DST begins and ends on statutorily mandated dates). There are two ways in which an area can be moved from one time zone to another: by regulation or by statute.

Under the Standard Time Act of 1918, as amended by the Uniform Time Act of 1966, moving a state or an area within a state from one time zone to another requires DOT regulation. Such a request can be made only by certain political authorities in an area.⁸¹ For example, if the request to change time zone is from one or more counties, the board (or boards) of county commissioners would make the request. If the request is for a state, the governor or the legislature would make the request.

DOT considers certain factors in making its decision on time zone change proposals.⁸² The principles for deciding whether to change the time zone for an area are the "convenience of commerce and the existing junction points and division points of common carriers engaged in interstate or foreign commerce."⁸³ The standard for deciding whether to change a time zone includes consideration of all the impacts upon a community that is requesting a change in its standard of time. The "convenience of commerce" is defined broadly to consider such circumstances as the shipment of goods within the community; the origin of television and radio broadcasts; the areas where most residents work, attend school, worship, or receive health care; the location of airports, railways, and bus stations; and the major elements of the community's economy.⁸⁴

After receiving a request, DOT determines whether it meets the minimum statutory criteria before issuing a notice of proposed rulemaking, under which it would solicit public comment and schedule a public hearing. Historically the hearing has been held in the area requesting the change so that affected parties can be represented. After the comment period closes, comments are reviewed and final action is taken. If the Secretary of Transportation agrees that the statutory requirement has been met, the change would be instituted, usually at the next changeover to or from DST.⁸⁵

In 2022, the DOT Office of Inspector General (OIG) conducted an audit of DOT processes for evaluating and responding to time zone change requests and DST exemptions.⁸⁶ DOT OIG found that DOT did not have written guidance on how time zone change petitions would be evaluated and validated.⁸⁷ DOT OIG issued five recommendations "to improve DOT's evaluation of time zone changes and promotion of uniform time observance"—all five recommendations were listed as closed as of January 15, 2025.⁸⁸

Selected State Actions to Change DST Observance

Even though a state cannot unilaterally adopt permanent year-round DST, a majority of states have initiated efforts to change the summer observance of DST. Many state legislative actions have occurred since 2015.⁸⁹ As of April 2026, CRS identified 47 states that have introduced legislation that would support changes to the summer observance of DST.⁹⁰ All 47 states have introduced legislation proposing some variation of permanent DST.⁹¹ Forty-two of these states have also introduced legislation to establish permanent standard time. Eight of these states have introduced legislation to study the effects of DST or the effects of changing the observance of DST.

Some of the state legislative proposals would be contingent upon the actions of neighboring states. For example, Idaho's S.B. 1267 (2020) would require the entire state to observe permanent DST "at such time as the state of Washington makes daylight saving time the permanent time of the state and all of its political subdivisions,"⁹² and Delaware's S.B. 73 (2019) would place the state in the Atlantic Standard Time zone if Pennsylvania, New Jersey, and Maryland enact similar legislation. Both the Idaho and Delaware bills have been enacted and signed into law. Since 2021, at least 10 additional states have introduced similar conditional legislation that would be contingent upon the actions of specific or unnamed neighboring states.⁹³

In addition, five states in New England—Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont—have created commissions to examine potential impacts of permanent DST or introduced proposals to move to year-round DST.⁹⁴ These proposals would change the standard time zone from Eastern Standard Time to Atlantic Standard Time (i.e., one hour ahead), which would effectively adopt DST all year round.⁹⁵ In November 2017, the Massachusetts Special Commission on the Commonwealth's Time Zone submitted its recommendation "that under certain circumstances the Commonwealth could make a data-driven case for moving to the Atlantic Time Zone year-round (effectively observing year-round DST)."⁹⁶

CRS identified 19 states that have enacted permanent DST legislation since 2018.⁹⁷ These include the following states (with year of enacted legislation):

• Florida (2018);
• Delaware, Maine, Oregon, Tennessee, and Washington state (2019);
• Idaho, Louisiana, South Carolina, Utah, and Wyoming (2020);
• Alabama, Georgia, Minnesota, Mississippi, and Montana (2021);
• Colorado (2022);
• Oklahoma (2024); and
• Texas (2025).

Three states have adopted nonbinding resolutions regarding permanent DST. Arkansas adopted H.R. 1034, a nonbinding resolution to establish permanent DST, on March 12, 2019. Georgia adopted H.R. 1240, a nonbinding resolution to urge the federal government to allow states to switch to permanent DST, on March 9, 2020.⁹⁸ Ohio adopted S.C.R. 8, "to urge Congress to enact [t]he [federal] Sunshine Protection Act of 2019 [H.R. 1556]," which would permanently extend daylight saving time, on December 3, 2020.

Two states have enacted legislation to study the effects of permanent DST. Massachusetts enacted H.B. 4569, to study the practical, economic, fiscal, and health-related impacts of the commonwealth remaining on eastern daylight time throughout the calendar year, on August 10, 2016.⁹⁹ Maine enacted L.D. 826, to study the potential effects of the state adopting Atlantic Standard Time, on June 22, 2021.¹⁰⁰

Maps identifying states that have introduced legislation proposing changes to the summer observance of DST, enacted such legislation, or have proposed to study the effects of DST are provided in Figure A-1 and Figure A-2.

Other actions to establish permanent DST or permanent standard time include statewide ballot measures. Some states have held elections to consider a ballot measure (e.g., California¹⁰¹) or have initiated and considered ballot initiatives to appear in general statewide elections (e.g., Colorado,¹⁰² Missouri,¹⁰³ and Texas¹⁰⁴).

Although the Uniform Time Act of 1966, as amended, allows for state exemptions from the seasonal observance of DST, state adoption of permanent year-round DST would be contingent upon congressional action.

Selected International DST Policies

The DST observance policies of other countries may be of interest to some Members of Congress. Some countries have temporary, seasonal advancement of standard time similar to DST; other countries (e.g., China, India, and Russia) do not seasonally adjust the observance of time. According to a 2023 analysis, approximately one-third of countries globally observe DST, with many of these DST-observing countries located in Europe and North America.¹⁰⁵ Some countries and governments that observe DST have considered whether to continue temporary observance of DST. Some jurisdictions have acted to discontinue the observance of DST. A few examples from entities that are large trade partners with the United States are discussed below.¹⁰⁶

The initial adoption of DST in the United States was preceded by adoption of DST in Europe, where it continues to be observed seasonally with some exceptions. In all member states of the European Union (EU), the time period for DST (referred to as the "summer-time period") begins at 1:00 a.m. Greenwich Mean Time (GMT) on the last Sunday in March and ends at 1:00 a.m. GMT on the last Sunday in October.¹⁰⁷ On March 26, 2019, the European Parliament voted in favor of a proposal to discontinue the seasonal observance beginning in 2021.¹⁰⁸ The proposal would have allowed EU member states to decide whether to advance to summer time in March 2021 and remain in summer time thereafter, or to revert to standard time ("winter time") in October 2021 and remain in winter time thereafter. Member states were to have notified the European Commission (the EU's executive body) by April 1, 2020, of the decision to observe summer time or winter time.¹⁰⁹ According to the text approved by the European Parliament, the decision should account for "citizens' preferences, geographical variations, regional differences, standard working arrangements and other factors." The proposal includes an option for postponing the application date for no more than 12 months to protect the functioning of the internal market (the market within the EU). The proposal also requires an assessment of the application and implementation of the directive to be submitted to the European Parliament and to the Council of the EU (in which the member states are represented) by December 31, 2025. On October 23, 2025, the European Parliament held a debate in plenary that discussed whether to discontinue the seasonal time change, and the Commission decided to study the issue further.¹¹⁰ The Council would also need to approve the proposal to end the seasonal time change for it to take effect as EU law. Without both the Council and the European Parliament in agreement to pass the legislation to end seasonal time changes, the EU continues the seasonal observance of DST.

Canada generally observes DST according to the same schedule as the United States. On March 8, 2026, as most regions in Canada temporarily set their clocks one hour ahead of standard time, most parts of the province of British Columbia adopted permanent year-round DST.¹¹¹ This time, referred to as "Pacific Time," is effectively consistent with Mountain Standard Time. British Columbia has the authority to adopt permanent DST through a provincial law, the Interpretation Amendment Act, which was enacted in 2019.¹¹²

In 2022, Mexico's congress passed and President López Obrador enacted legislation that ended the observance of DST (referred to as "horario de verano") in most areas of the country.¹¹³ The law, which went into effect on October 30, 2022, provides for exceptions for areas along the U.S. border to observe temporary DST from the second Sunday in March at two o'clock ante meridian (2:00 a.m.) to the first Sunday in November at 2:00 a.m.¹¹⁴

Potential Issues for Congress

Congress may again consider whether to make changes to DST observance or standard time. Considerations could include maintaining DST year-round, maintaining standard time year-round, or maintaining the current status quo of alternating between the two. In the 119^th Congress, several bills would address DST observance. One bill, the Sunshine Protection Act of 2025 (H.R. 139 and S. 29), as introduced, would advance standard time by one hour to effectively establish permanent DST (with some options for exemptions). On May 21, 2026, the House Committee on Energy and Commerce voted in favor of H.R. 7389, the Motor Vehicle Modernization Act of 2026—which, as ordered to be reported as amended, includes the Sunshine Protection Act of 2025. After the committee vote, President Trump expressed support for the Sunshine Protection Act of 2025.¹¹⁵ On July 14, 2026, the House passed H.R. 139, with a roll call vote of 309-117.

Several other bills introduced in the 119^th Congress also propose changes to the observance of DST. Bills such as the Daylight Act (H.R. 300) and H.R. 1630—"To allow States to elect to observe year-round daylight saving time, and for other purposes"—would allow states to opt for permanent DST. Another bill, the Daylight Act of 2026 (H.R. 7378), would repeal DST and advance standard time by 30 minutes. The Sunshine for Our Kids Act of 2026 (H.R. 9638) would repeal DST, effectively implementing year-round standard time.

Versions of the Sunshine Protection Act of 2025 have been introduced in previous Congresses. The Sunshine Protection Act of 2018 (H.R. 5279 and S. 2537) was first introduced in the 115^th Congress. In the 117^th Congress, the Sunshine Protection Act of 2021 (S. 623) passed the Senate with an amendment by unanimous consent.¹¹⁶ The bill was reintroduced in the 118^th Congress (H.R. 1279 and S. 582) and 119^th Congress (H.R. 139 and S. 29).

Congress could consider further study or request additional information on the benefits and costs of the different options. Options could include authorizing federal agencies to study the effects of different options as Congress has previously requested of DOT in the 1970s and DOE in the 2000s. In the 115^th Congress, the House Committee on Energy and Commerce sent a letter to DOT requesting updated information related to DST and standard time "to more fully appreciate the various policy factors associated with changing between Standard and [DST]."¹¹⁷ DOT responded to the committee with a letter on June 20, 2018, stating the Department has "initiated a literature review of this issue" and it "will share the results" once completed.¹¹⁸ As of July 2026, CRS could not confirm whether the results of the literature review had been shared with the committee. In the 119^th Congress, the Senate Committee on Commerce, Science, and Transportation held a hearing to consider issues related to the nation's observance of time.¹¹⁹

In the consideration of federal policies for DST, Congress may consider which states observe DST and whether states would change their DST observance if federal policy were to change. In addition, Congress may consider how other federal policies might influence state decisionmaking on DST observance. For example, in the 119^th Congress, the Take Care of America's Veterans Act (H.R. 9237 and S. 4744) would, among other provisions, direct the Secretary of Veterans Affairs to ensure that the Veterans Health Administration has call centers in certain time zones, with an exception for any location generally "that does not follow daylight saving time." Whether states are eligible for federal programs or services contingent upon DST observance could introduce additional complexities to the issue of DST.

Appendix. Timeline and Maps

Figure A-1. State Permanent DST Legislation or Study Effects of DST States with Introduced and Enacted Legislation (January 2015-April 2026)

Source: CRS based on Lexis Advance database ("Statutes and Legislation" database); state legislature websites/databases; National Council of State Legislature's (NCSL's) Daylight Saving Time | State Legislation resource; CQ.com's Policy Note (formerly the Fiscal Note) database. Notes: Legislative efforts by states were identified in database searches conducted on May 22, 2018; May 17, 2019; July 15, 2020; December 2, 2021; February 21, 2022; and April 24, 2026. Nonbinding refers to a nonbinding resolution that was adopted in support of establishing permanent DST. AL: Alabama's House and Senate passed S.B. 388 ("Daylight Savings Time, adopted statewide if Congress amends Federal law to allow") and the bill was signed into law by Governor Kay Ivey on May 6, 2021. AR: Arkansas adopted H.R. 1034, a nonbinding resolution to establish permanent DST, on March 12, 2019. CO: Colorado's House and Senate passed H.B. 22-1297 ("Daylight Saving Time Year Round") and the bill was signed into law by Governor Jared Polis on June 2, 2022. DE: Delaware's House and Senate passed S.B. 73 ("An Act to Adopt Eastern Daylight Time Year-Round") and the bill was signed into law by Governor John Carney on August 12, 2019. The bill requires the governor to request that the U.S. Secretary of Transportation place Delaware in the Atlantic Standard Time zone if Pennsylvania, New Jersey, and Maryland each do the same. FL: Florida's House and Senate passed H.B. 1013 ("Sunshine Protection Act"), and the bill was approved by Governor Rick Scott on March 23, 2018. The bill would institute year-round DST in Florida "if the United States Congress amends 15 U.S.C. §260a to authorize states to observe daylight saving time year-round." GA: Georgia's House of Representatives adopted nonbinding resolution H.R. 1240, to urge the federal government to allow states to switch to permanent DST, on March 9, 2020. In 2021, Georgia's House and Senate passed S.B. 100, which would establish DST as the official time year-round, subject to congressional authorization. Governor Brian Kemp signed the bill into law on April 21, 2021. ID: Idaho's House and Senate passed S.B. 1267 and Governor Brad Little signed the bill into law on March 16, 2020. The law would make DST the permanent time for all political subdivisions of Idaho in the Pacific time zone ("at such time as the state of Washington makes daylight saving time the permanent time of the state and all of its political subdivisions") if Congress amends federal law to allow. Regions of the state in the Mountain time zone would not be affected. LA: Louisiana's House and Senate passed H.B. 132, which establishes DST as the official time year-round, subject to an authorizing federal law. Governor John Bel Edwards signed the bill into law on June 9, 2020. MA: Massachusetts's House and Senate passed H.B. 4569. Section 136 of the bill commissioned a comprehensive study of the practical, economic, fiscal, and health-related impacts of the commonwealth remaining on Eastern Daylight Time throughout the calendar year. Governor Charlie Baker signed the bill into law on August 10, 2016. ME: Maine's House and Senate passed H.P. 659 (L.D. 885), an act "To Adopt Eastern Daylight Time Year-Round." Governor Janet Mills received the passed legislation on June 11, 2019, which became law without the governor's signature. In 2021, Maine's House and Senate passed L.D. 826, to study the potential effects of the state adopting Atlantic Standard Time. Governor Janet Mills signed the bill into law on June 22, 2021. MN: Minnesota's House and Senate passed S.F. 2a, "providing for advanced standard time, also known as DST, year-round effective upon authorization by federal law." Governor Tim Walz signed the bill into law on June 30, 2021. MS: Mississippi's House and Senate passed H.B. 1062, to observe year-round daylight saving time if federal law is amended to allow it. Governor Tate Reeves signed the bill into law on March 17, 2021. MT: Montana's House and Senate passed S.B. 254, which would authorize year-round Mountain Daylight Time contingent on approval by U.S. DOT or Congress and similar action in other states. The bill exempts the state and its political subdivisions from Mountain Standard Time; Governor Greg Gianforte signed the bill into law on May 10, 2021. OH: Ohio's House and Senate adopted S.C.R. 8, a nonbinding resolution to urge Congress to enact the federal Sunshine Protection Act of 2019 (H.R. 1556), on December 3, 2020. The federal bill would permanently extend daylight saving time. OK: Oklahoma's House and Senate passed S.B. 1200 ("An Act enabling Oklahoma to adopt daylight saving time as the year-round time upon certain authorization") and the bill was signed into law by Governor Kevin Still on April 26, 2024. OR: Oregon's House and Senate passed S.B. 320, which abolishes the annual change in time from standard time to DST and maintains Oregon on DST. The bill refers the act to the people of Oregon for their approval or rejection at the next regular general election. Governor Kate Brown signed the bill into law on June 17, 2019. SC: South Carolina's House and Senate passed S.11 and Governor Henry McMaster signed the bill into law on February 7, 2020. The bill would make DST the year-round standard time for the entire state if the U.S. Congress amends related federal law to allow states to observe DST year-round. TN: Tennessee's House and Senate passed H.B. 247 and Governor Bill Lee signed the bill on May 8, 2019. H.B. 247 would establish "daylight saving time as the standard time in Tennessee," subject to authorization to do so from the U.S. Congress. TX: Texas's House and Senate passed H.B. 1393 and Governor Greg Abbott signed the bill on June 20, 2025. This enacted law would take effect September 1, 2025, but only if the U.S. Congress enacts legislation that becomes law that authorizes the State of Texas to observe daylight saving time year-round. UT: Utah's Senate and House passed S.B. 59 and Governor Gary Herbert signed the bill into law on March 28, 2020. The bill, subject to congressional authorization, would "place Utah and all political subdivisions in Utah on year-round mountain daylight time." WA: Washington's House and Senate passed H.B. 1196 ("Allowing for the year round observation of daylight saving time") and the bill was signed into law by Governor Jay Inslee on May 8, 2019. The bill is subject to the U.S. Congress amending federal law and authorizing states to observe DST year-round. WY: Wyoming's House and Senate passed H.B. 44 and Governor Mark Gordon signed the bill into law on March 24, 2020. The bill, subject to congressional authorization, would authorize the entire state of Wyoming to observe Mountain Daylight Time.

Figure A-2. State Permanent Standard Time Legislation States with Introduced Legislation (January 2015-April 2026) Source: CRS based on Lexis Advance database ("Statutes and Legislation" database); state legislature websites/databases; National Council of State Legislature's (NCSL's) Daylight Saving Time | State Legislation resource; CQ.com's Policy Note (formerly the Fiscal Note) database. Notes: Legislative efforts by states were identified in database searches conducted on May 22, 2018; May 17, 2019; July 15, 2020; December 2, 2021; February 21, 2022; and April 24, 2026. No state has enacted legislation for permanent standard time between January 2015 and April 2026.

Footnotes