As fall settles in across the United States, many Americans are preparing to adjust their clocks as daylight saving time (DST) comes to an end. On Sunday, November 2, 2024, at 2 a.m. local time, clocks will be set back one hour, marking the return to standard time. This annual ritual, commonly known as “falling back,” signals shorter daylight hours in the evening and earlier sunsets. While this change may seem minor, it has far-reaching effects on sleep patterns, public health, and even politics.
### The Basics of Daylight Saving Time in the U.S.
Daylight saving time in the U.S. officially ends on the first Sunday of November, specifically at 2 a.m., when clocks are turned back one hour. The time change will remain in effect until the second Sunday of March, 2025, when the clocks will “spring forward” again at 2 a.m., marking the start of DST. This cyclical pattern means that for about eight months of the year, Americans live on daylight saving time, and for the remaining four months, they observe standard time.
The practice of adjusting clocks forward in spring and back in fall is intended to make better use of daylight during the longer days of summer. However, the start and end dates of DST are not fixed to specific calendar days; rather, DST begins on the second Sunday in March and ends on the first Sunday in November. This schedule was established by the Uniform Time Act of 1966, which sought to bring consistency to what had been a patchwork of local and state time changes.
### A Historical Perspective on Time Zones and DST
The concept of standardized time zones in the United States dates back to the railroad boom of the late 19th century. Before then, towns and cities set their clocks based on local solar time, which created confusion for train schedules and commerce. The introduction of time zones helped synchronize activities across regions.
Daylight saving time itself was first nationally introduced in 1918 but was applied inconsistently in the following decades. The Uniform Time Act of 1966 finally standardized the start and end dates for DST across the country. One notable experiment with year-round daylight saving time occurred in 1974 during the energy crisis under President Richard Nixon. The idea was to conserve energy by extending evening daylight, but the policy proved unpopular, particularly because it meant very dark mornings, and was reversed by Congress and President Gerald Ford later that year.
### States and Territories Without Daylight Saving Time
Not all parts of the U.S. observe daylight saving time. Arizona (except for the Navajo Nation) and Hawaii remain on standard time year-round, avoiding the disruption of clock changes altogether. Additionally, U.S. territories such as Puerto Rico, Guam, the Virgin Islands, American Samoa, and the Northern Mariana Islands also do not participate in DST.
For residents in these areas, the benefits include avoiding the physical and mental health impacts associated with the biannual clock changes. These health concerns have become a major point of discussion in recent years, leading to calls for reform or outright abolition of daylight saving time.
### Health and Safety Concerns
The time change is notorious for disrupting people’s internal body clocks, or circadian rhythms, which can negatively impact physical and mental health. Organizations such as the National Sleep Foundation, the American Academy of Sleep Medicine, and the Society for Research on Biological Rhythms advocate for permanent standard time, citing its alignment with human biology.
Joseph Dzierzewski, senior vice president of research and scientific affairs at the National Sleep Foundation, highlights several concerns associated with daylight saving time. These include increased risks of cardiovascular events, mental health challenges, and a rise in drowsy driving incidents immediately following time changes. Safety issues also extend to children who may have to travel to school or wait at bus stops in the dark during the darker mornings of DST, a significant factor that contributed to the repeal of year-round daylight saving time in the 1970s.
### Public Opinion and Political Efforts
Public sentiment largely favors ending the biannual clock changes. A YouGov poll conducted in October 2024, surveying over 1,100 U.S. adults, found that 63% of respondents want to eliminate the clock changes entirely. Only 17% wished to keep the current system, while 20% were undecided.
Despite this majority, legislative efforts to end time changes have repeatedly stalled. The Sunshine Protection Act,