Daylight Saving Time: Which Countries Change Their Clocks?

Daylight Saving Time (DST) is the practice of setting clocks forward by one hour in spring and back by one hour in autumn to make better use of daylight during the longer days of summer. About 70 countries observe some form of DST, but the majority of the world's nations do not, and the practice is increasingly controversial even in countries that use it.

Introduction

The geography of DST follows a clear pattern: it is primarily used in countries at higher latitudes in the Northern Hemisphere, where the difference in daylight between summer and winter is most dramatic. Countries near the equator, where daylight hours barely change throughout the year, have little reason to shift their clocks.

Who Observes DST?

• Total Countries: ~70
• North America: USA (most states), Canada (most provinces), Mexico (ended 2022)
• Europe: All EU/EEA countries (proposal to end it stalled)
• Southern Hemisphere: Australia (some states), New Zealand, Chile, Paraguay

DST is most consistently observed across Europe and North America. All European Union member states change their clocks, though a 2019 EU proposal to abolish DST received 84% public support but has been stalled in implementation ever since. The United States observes DST in all states except Arizona (excluding the Navajo Nation) and Hawaii.

In the Southern Hemisphere, DST is observed in reverse: clocks go forward in October and back in March/April. Australia's DST situation is particularly complex, with New South Wales, Victoria, Tasmania, South Australia, and the ACT observing it while Queensland, Western Australia, and the Northern Territory do not.

Who Doesn't Observe DST?

• Most of Africa: Only Morocco observes DST
• Most of Asia: Japan, China, India, and most others do not
• Tropical Countries: Generally no DST (daylight barely varies)
• Countries That Stopped: Russia (2014), Turkey (2016), Mexico (2022)

Most countries near the equator do not observe DST because the length of their days barely changes throughout the year. Countries like Singapore, Malaysia, and Indonesia have roughly 12 hours of daylight year-round, making clock changes pointless.

Several countries have recently abandoned DST. Russia permanently stayed on "summer time" in 2011, then switched to permanent "winter time" in 2014. Turkey adopted permanent summer time in 2016. Mexico abolished DST in 2022 (except in border cities near the US). The trend in recent decades has been away from DST, not toward it.

The Energy Debate

• Original Claim: DST saves energy by reducing lighting needs
• Modern Studies: Energy savings are minimal or non-existent
• Air Conditioning: May actually increase energy use in warm climates
• Indiana Study: DST increased energy costs by $9 million/year

DST was first widely adopted during World War I to save coal for the war effort by reducing the need for artificial lighting in the evenings. The energy-saving argument persisted for decades, but modern studies have largely debunked it. A comprehensive study in Indiana found that DST actually increased residential electricity consumption by about 1%, costing the state an extra $9 million per year.

The problem is that while DST may reduce lighting costs, it increases air conditioning use because people are awake during hotter evening hours. In modern economies where lighting is a small fraction of energy use and cooling is significant, the original rationale for DST no longer holds.

Health and Safety Effects

• Heart Attacks: 19% increase in Monday after spring forward
• Car Accidents: 6% increase in the week after spring forward
• Sleep Disruption: Takes 1-2 weeks to fully adjust
• Workplace Injuries: Increase noted in mining and construction data

The health effects of the biannual clock change are well-documented and concerning. A 2014 study in the journal Open Heart found a 24% increase in heart attacks on the Monday after the spring time change. Car accidents spike by about 6% in the week following the spring change, attributed to sleep-deprived drivers.

The disruption to circadian rhythms affects most people for at least a few days and some for up to two weeks. Sleep researchers have increasingly called for the abolition of DST, arguing that the biannual clock change is a public health hazard with no meaningful economic benefit to offset the risks.

The Future of DST

• EU Proposal: 2019 vote to end DST, implementation stalled
• US Sunshine Protection Act: Passed Senate 2022, stalled in House
• Trend: More countries abandoning DST each decade
• Expert Opinion: Sleep scientists favor permanent standard time

The global trend is clearly moving away from DST. The European Parliament voted in 2019 to allow each member state to choose permanent summer or winter time, but disagreements about which to choose have stalled implementation. In the US, the Sunshine Protection Act to make DST permanent passed the Senate unanimously in 2022 but has not passed the House.

Sleep scientists and chronobiologists generally favor permanent standard time (winter time) over permanent DST, arguing that standard time more closely aligns with the body's natural circadian rhythm. The debate is not really about whether to change clocks, most experts agree that should stop, but about which time to keep permanently.

Key Facts

• About 70 countries observe DST, primarily at higher latitudes in the Northern Hemisphere.
• Countries near the equator generally do not observe DST because daylight hours barely change.
• Modern studies show DST saves little or no energy and may actually increase consumption.
• Heart attacks increase by 24% on the Monday after the spring time change.
• The global trend is toward abolishing DST, with Russia, Turkey, and Mexico among recent examples.

Fun Facts

• Benjamin Franklin suggested something like DST in a 1784 satirical essay about Parisians sleeping through morning sunlight.
• Germany was the first country to adopt DST in 1916 during World War I.
• Arizona doesn't observe DST, but the Navajo Nation within Arizona does, and the Hopi Reservation within the Navajo Nation doesn't.
• In 2019, 84% of EU citizens surveyed wanted to abolish the biannual clock change.

Final Thoughts

Daylight saving time is one of geography's most debated practices. Originally adopted to save energy in wartime, it persists despite mounting evidence that its costs, in health, safety, and disruption, outweigh its benefits. The geographic pattern of DST use reveals a clear latitude effect, but the growing global trend toward abolition suggests that the biannual clock change may not survive much longer.