Daylight Saving Time (DST) is the practice of setting clocks forward one hour from standard time during warmer months and back again in the autumn. The idea is to make better use of natural daylight. Moving clocks forward in the spring gives us more daylight in the evenings, while moving them back in the autumn provides more daylight during winter mornings.
Daylight Saving Time in the United States begins on the second Sunday in March and ends on the first Sunday in November. To remember which way to adjust clocks, people often use the saying “spring forward, fall back.”
Daylight Saving Time starts at 2:00 AM on the designated Sunday in March. Clocks are moved forward one hour, effectively losing an hour. This results in sunrise and sunset occurring about an hour later than the previous day, providing more light in the evening. Conversely, Daylight Saving Time ends at 2:00 AM on the designated Sunday in November. Clocks are set back one hour, gaining an hour. This leads to sunrise and sunset happening about an hour earlier, resulting in more light in the morning. Since the time change happens at 2:00 AM, most people adjust their clocks before going to bed on Saturday night.
There are exceptions to Daylight Saving Time within the U.S. These include Arizona (except for the Navajo Nation), Hawaii, Puerto Rico, the U.S. Virgin Islands, Northern Mariana Islands, Guam, and American Samoa. It’s important to note that these dates apply to the United States and Canada. Other countries may observe Daylight Saving Time on different dates. The correct term is “Daylight Saving Time,” not “Daylight Savings Time,” although the latter is a common mistake. “Saving” is singular because it functions as part of an adjective, not a verb.
During the period when Daylight Saving Time is in effect (from March to November), the time is referred to as “Daylight Time” (DT). When Daylight Saving Time ends, we revert to “Standard Time” (ST). Time zone abbreviations also change to reflect this. For example, Eastern Daylight Time (EDT) becomes Eastern Standard Time (EST) after Daylight Saving Time ends. Other examples include Central Daylight Time (CDT) changing to Central Standard Time (CST), Mountain Daylight Time (MDT) to Mountain Standard Time (MST), and Pacific Daylight Time (PDT) to Pacific Standard Time (PST).
The concept of Daylight Saving Time dates back to Benjamin Franklin, who humorously suggested in 1784 that people should wake up at dawn to save on candlelight. However, the first serious advocate for Daylight Saving Time was William Willet, a British builder who proposed shifting clocks forward in the summer to take advantage of daylight hours. His idea initially faced ridicule but gained traction during World War I as a way to conserve energy. Germany adopted Daylight Saving Time in 1915, followed by Britain in 1916 and the United States in 1918.
Contrary to popular belief, farmers were strong opponents of Daylight Saving Time. They argued that it disrupted their work schedules and did not benefit them. After World War I, opposition from farmers led to the repeal of Daylight Saving Time in the U.S. in 1920. It was reinstated during World War II and has been used on and off ever since. Inconsistencies in how states observed Daylight Saving Time led to confusion, prompting Congress to pass the Uniform Time Act in 1966 to standardize its use. However, some states still have exemptions. In 1986, the start date was moved to the first Sunday in April to conserve energy. The current Daylight Saving Time schedule, starting on the second Sunday in March and ending on the first Sunday in November, was established by the Energy Policy Act of 2005.
Despite its energy-saving goals, Daylight Saving Time remains controversial. Farmers continue to oppose it, and some research suggests it may have negative impacts on health and safety. As of 2023, several states have passed legislation to make Daylight Saving Time permanent, but this requires a change in federal law. The debate over whether to continue or abolish the practice of changing clocks twice a year is ongoing.