Both permanent standard time and permanent daylight saving time (DST) eliminate the practice of semi-annual clock changes, specifically the advancement of clocks by one hour from standard time to DST in spring (commonly called "spring forward") and the retraction of clocks by one hour from DST to standard time in fall ("fall back").
The Uniform Time Act of 1966 formalized the specification of time zones and the dates of DST observation in the United States. Prior to this law, time zones and DST observation in America were independent and erratic across states and cities. The law requires states to change clocks semiannually between standard time and DST on federally mandated dates, and it permits states to opt out of DST observation altogether and remain on permanent standard time, but does not permit observation of permanent DST. Arizona (with the exception of the Navajo Nation), Hawaii, and all permanently inhabited territories observe permanent standard time.
Studies have shown the semi-annual clock changes result in sleep disturbances, ultimately resulting in more health problems and traffic accidents. Legislators in 25 states have attempted to switch to either permanent standard time or permanent DST. Currently more states are pursuing permanent DST.
Permanent standard time
Prior to the nationwide implementation of DST in 1967, some American states observed permanent Standard Time. Currently in the US, Arizona (with the exception of the Navajo Nation), Hawaii, and all permanently inhabited territories (American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands) observe permanent standard time. A number of states have proposed bills to restore observation of permanent standard time, but few have gained ground as of yet.
Possible benefits and disadvantages of standard time
Permanent standard time is considered by circadian health researchers and safety experts worldwide to be the best option for health, safety, schools, and economy, including the American Academy of Sleep Medicine, National Sleep Foundation, American College of Chest Physicians, National Safety Council, American College of Occupational and Environmental Medicine, Canadian Sleep Society, World Sleep Society, Society for Research on Biological Rhythms, and several state sleep societies. Permanent standard time is supported by advocates for school children, including the National PTA, National Education Association, American Federation of Teachers, National School Boards Association, and Start School Later. They cite both the health benefits of circadian alignment, and the safety advantages regarding morning commutes.
Permanent standard time is also supported by environmental data, owing to evidence that DST observation increases morning heating, evening driving, and evening residential air conditioning, which all in turn increase energy consumption and pollution.
Permanent daylight saving time
A change in federal law would be necessary to allow states to observe DST permanently all year. A number of states have pursued state bills, resolutions, and referendums to indicate intention to observe permanent DST if federal law would permit it.
In 2018, 2019, 2020, and 2021, Florida Republican Senator Marco Rubio introduced to Congress the "Sunshine Protection Act", a bill to permit states to observe permanent DST. The bill had achieved referral to committee, but had not received a hearing. Also in 2021, Florida Republican Representative Vern Buchanan introduced a daylight saving time for the whole country, by changing everyone's time zone forward by an hour (Eastern Time would become permanently UTC-0400 instead of UTC-0500). That bill also allowed states to opt out under certain conditions. On March 15, 2022, Rubio's bill passed the Senate.
As a work-around to the Uniform Time Act's prohibition on permanent DST, a bloc of states in New England has proposed a statutory move from the Eastern Time Zone to the Atlantic Time Zone (Atlantic Time being one hour ahead of Eastern Time), and then abolishing biannual clock changes. If approved by the Department of Transportation, such a move would effectively put these states on permanent DST without needing to await amendment to the Uniform Time Act by Congress. Similarly, on the West Coast, Washington passed both a bill for permanent DST and an alternative bill to move the state's official observation from the Pacific Time Zone to the Mountain Time Zone.