What Is Daylight Saving Time?
Daylight Saving Time (DST) sets clocks forward by one hour during the warmer months so evening daylight lasts longer. The US follows it from 2:00 AM on the second Sunday in March until 2:00 AM on the first Sunday in November.
Here's how it works in practice. On Sunday, March 8, 2026, at 2:00 AM, clocks in Washington jump straight to 3:00 AM. You lose an hour of sleep. On Sunday, November 1, 2026, at 2:00 AM, they fall back to 1:00 AM. You gain an hour back.
The shift is simultaneous across all observing US zones. When Eastern clocks spring forward at 2:00 AM, it's 1:00 AM in Central, 12:00 AM in Mountain, and 11:00 PM the previous day in Pacific.
When Does DST Start and End? Current Schedule
The current federal schedule:
- DST begins: Second Sunday in March at 2:00 AM local time
- DST ends: First Sunday in November at 2:00 AM local time
For 2026, that means:
- Spring forward: Sunday, March 8, 2026 at 2:00 AM → 3:00 AM
- Fall back: Sunday, November 1, 2026 at 2:00 AM → 1:00 AM
For 2027:
- Spring forward: Sunday, March 14, 2027 at 2:00 AM → 3:00 AM
- Fall back: Sunday, November 7, 2027 at 2:00 AM → 1:00 AM
The transition happens at the same absolute moment nationwide, but the local clock time differs by zone. When Eastern springs forward at 2:00 AM ET, it's 1:00 AM CT, 12:00 AM MT, and 11:00 PM PT (the previous day).
Spring Forward, Fall Back: How the Clock Change Works
The mechanics of the clock change create odd temporal artifacts.
The spring-forward Sunday is only 23 hours long. The fall-back Sunday runs 25 hours. That extra hour in the first Sunday of November means 1:00 AM happens twice, once before the change, once after. You live through the same 60-minute stretch twice.
These aren't just curiosities. They affect payroll systems, software timestamps, and anyone scheduling across time zones. A meeting at 1:30 AM on a fall-back Sunday is genuinely ambiguous, it happens twice.
The practical takeaway: if you're scheduling anything in the 1:00 AM, 2:00 AM window on the first Sunday of November, specify whether you mean before or after the change.
Why Do We Have Daylight Saving Time? The Original Rationale
The idea predates the US federal system. Benjamin Franklin famously joked about it in 1784, but the serious push came during World War I.
Germany was first to adopt DST nationally in 1916, hoping to save coal. The US followed in 1918 with the Standard Time Act, which created federal time zones and introduced DST as a wartime fuel-saving measure.
Here's what most people get wrong: the original rationale was energy conservation, not farming. The country needed to reduce artificial lighting use and free up resources for the war effort.
The 1918 law was so unpopular, especially with agricultural communities, that Congress repealed DST in 1919, overriding President Wilson's veto. What followed was chaos.
Does DST Actually Save Energy? What Studies Show
The evidence is mixed at best.
The US Department of Energy studied the 2007 extension and found DST reduces electricity use by about 0.5% per day. That sounds small. Other studies are less kind. Research in Indiana found DST actually increased residential electricity demand by 1-4%, particularly in the fall when mornings get darker and people heat their homes in the dark.
The problem is that modern energy use doesn't track sunlight the way it did in 1918. We don't just use electricity for lighting anymore. Heating, cooling, and electronics follow different patterns. The energy argument for DST is weaker now than it's ever been.
The Uniform Time Act of 1966: Federal DST Rules
The chaos period between 1919 and 1966 was exactly what it sounds like. No federal DST law meant states and localities set their own dates. Iowa had 23 different DST start dates in a single year.
The Uniform Time Act of 1966 fixed the worst of this. It established uniform DST start and end dates nationwide, last Sunday in April to last Sunday in October, and gave the Department of Transportation authority over time zones.
Crucially, the act included an opt-out clause. States could exempt themselves from DST entirely. The Grand Canyon State and Hawaii took that option almost immediately.
The act also set the rule that still governs today: states cannot independently adopt permanent DST. Only Congress can change the federal DST framework.
The Energy Policy Act of 2005: The 2007 Extension
The current schedule came from the Energy Policy Act of 2005, which extended DST by about four weeks starting in 2007.
The new dates moved DST start from the first Sunday in April to the second Sunday in March, and the end from the last Sunday in October to the first Sunday in November.
The stated rationale was energy savings. The actual effects were modest. The Department of Energy estimated the extension reduced electricity use by 0.5% per day of DST, a figure that has been widely disputed.
Notably, this wasn't the first time the US experimented with extended DST. In 1974, during the OPEC oil embargo, President Nixon signed the Emergency Daylight Saving Time Energy Conservation Act, making DST year-round. It was so unpopular, children walked to school in darkness, that Congress repealed it after one season.
States That Don't Observe DST
Two states don't change their clocks. That's the simple version. The full story has more texture.
Hawaii has never observed DST since the Uniform Time Act passed. The state sits near the equator, sunrise and sunset barely shift across the year, so DST buys nothing. Hawaii stays on Hawaii Standard Time (HST, UTC-10) year-round.
The state with the Grand Canyon is more complicated. It opted out in 1968, but the reasons are climatic, not astronomical. Summers there are brutally hot. Moving an hour of daylight to the evening means an extra hour of air conditioning use when the sun is highest. Staying on Mountain Standard Time (MST, UTC-7) keeps the hottest part of the day shorter in summer.
Here's the confusing part: in summer, that southwestern state is on the same time as Pacific Daylight Time (PDT, UTC-7), not Mountain Daylight Time (MDT, UTC-6). People say it's "on Pacific time in summer", technically false, but practically true.
The Navajo Nation Exception: A DST 'Donut'
The southwestern state's DST opt-out has a geographic hole in it. The Navajo Nation, which spans the northeastern corner of that state, northwestern New Mexico, and southeastern Utah, does observe DST.
So when the surrounding state is on standard time, the Navajo Nation is an hour ahead. When clocks spring forward, the Navajo Nation is on the same time as the rest of the state.
Inside the Navajo Nation sits the Hopi Reservation, which does not observe DST. The Hopi Reservation is completely surrounded by Navajo Nation land.
This creates a DST "donut." In summer, the sequence of time zones looks like this: the state (no DST), then Navajo Nation (DST), then Hopi Reservation (no DST), then back into Navajo Nation. You can drive through three different time offsets in under an hour without crossing a state line.
How DST Affects Health, Accidents, and Daily Life
The twice-yearly switch has documented negative effects. The evidence is consistent enough that the American Academy of Sleep Medicine has called for abolishing the time change entirely.
In the days after spring-forward, studies show a 6-8% increase in car accidents in the first few days and a measurable spike in heart attacks, particularly in the first two days. Workplace injuries also rise.
The fall-back transition is gentler, but it has its own effects. The extra hour of sleep initially reduces accident rates, but the early darkness contributes to seasonal affective disorder and evening accident risk.
The core problem is that DST forces a sudden shift in circadian rhythm. Your internal clock doesn't adjust to a one-hour change overnight. It takes days for your body to catch up.
Common DST Myths: Farmers and 'Daylight Savings'
Two myths dominate every DST conversation, and both are wrong.
Myth 1: "DST was created for farmers." False. Farmers were among the most vocal opponents of DST in 1918. Their schedules follow the sun, not the clock. Cows don't care what time the milking parlor says it is. The farming lobby pushed hard for the 1919 repeal.
Myth 2: "Daylight Savings Time" (with an 's'). The correct term is "Daylight Saving Time", singular. It's a common error, but it's wrong. The time is being saved, not the day.
Other misconceptions persist. DST is not about giving farmers more daylight, it's about shifting human activity to match daylight hours. And it's not about school children, school start times are set by local districts, not federal law.