Pros and Cons of Daylight Saving Time

Daylight Saving Time was originally adopted to save energy, but the debate has broadened well beyond lighting costs. Decades of research have examined DST's effects on health, safety, commerce, and daily life. The evidence is mixed — and the balance of trade-offs is central to the permanent DST vs. standard time debate.

Energy Savings

The argument for

The original logic: more evening daylight means less artificial lighting, saving electricity. When DST was first adopted in 1916, this was a meaningful saving — lighting was a large share of energy use, and it was all incandescent.

The evidence

A 2008 US Department of Energy study found the four-week DST extension (from the Energy Policy Act of 2005) saved about 0.5% of electricity per day, or roughly 1.3 billion kWh over the extended period. However, a 2011 study of Indiana — which had recently adopted statewide DST — found a 1–4% increase in residential electricity use, mainly from air conditioning.

The consensus: in moderate climates, DST produces a small lighting reduction. In hot climates, increased air conditioning can offset or exceed those savings. Modern LED lighting further reduces the potential benefit. Energy is no longer the strongest argument for or against DST.

Health Effects

Spring transition (losing an hour)

The spring "spring forward" is consistently associated with negative health outcomes in the days following the change:

• Heart attacks: A 2014 study in Open Heart found a 24% increase in heart attacks on the Monday after the spring transition.
• Sleep disruption: Most people take 2–5 days to fully adjust. Sleep loss is cumulative and affects cognitive function.
• Workplace injuries: A 2009 study in the Journal of Applied Psychology found an increase in workplace injuries and a decrease in sleep following the spring change.
• Mental health: Some studies link the spring transition to increased rates of depression and seasonal affective disorder symptoms.

Fall transition (gaining an hour)

The autumn "fall back" has fewer documented negative effects. Some studies show a slight decrease in heart attacks in the days after. The extra hour of sleep is generally welcomed, though the earlier darkness can contribute to seasonal mood changes.

Medical position

The American Academy of Sleep Medicine (AASM) has formally called for the elimination of seasonal clock changes, recommending permanent standard time as the healthier option, since it better aligns with natural circadian rhythms.

Traffic Safety and Crime

Traffic

More evening daylight is correlated with fewer pedestrian fatalities in the late afternoon and evening hours. However, the shift to darker mornings increases risk during the morning commute, particularly in northern states during March. The net effect on annual traffic fatalities is debated and likely small.

The spring transition itself is dangerous: the Monday after "spring forward" sees a measurable increase in car accidents, attributable to sleep deprivation.

Crime

A 2015 Brookings Institution study found a 7% decrease in robberies following the spring transition, attributed to more daylight during evening hours when street crime is more common. The effect is modest but consistent.

Economic Effects

Supporters argue that DST increases consumer spending: more evening daylight means more time for shopping, dining, and outdoor recreation. The retail, sports, and tourism industries have historically lobbied in favor of DST.

Critics point to the coordination costs of the transitions: schedule changes, software updates, confusion in international business (especially during the weeks when the US and Europe are on different DST schedules). Airlines adjust flight schedules, and the time-difference between countries on different DST rules creates temporary offsets.

Agriculture

Farmers have historically opposed DST. Livestock and crop schedules are governed by sunlight, not clocks. When DST was first adopted in the US in 1918, farming organizations led the campaign to repeal it, succeeding in 1919. The misperception that DST was created to help farmers is one of the most common DST myths.

Summary

Last reviewed: March 2026. Data sources: official government publications and worldwideclock.com.