Science Vs – Daylight Saving Time: Should We End It?

Host: Michelle Deng (filling in for Wendy Zuckerman)
Date: October 30, 2025
Duration (content): ~00:00–33:33

Episode Overview

This episode of Science Vs investigates whether we should stop changing our clocks twice a year for Daylight Saving Time (DST). Host Michelle Deng, alongside senior producer Meryl Horne, dives into the history, intended benefits, and real-world consequences of DST. The episode weighs scientific evidence for and against sticking with either permanent Standard Time or DST year-round, asking: what’s healthiest, safest, and most practical for society?

Key Discussion Points and Insights

1. The Origins and Persistence of Daylight Saving Time

[03:40 – 06:25]

• Origins:

  • Contrary to popular belief, DST was not invented for farmers. It originated as an energy-saving policy during World War I, first adopted by Germany.
    • Michelle Deng [04:19]:
      “It actually started as a government project to save energy…and this was back during the World War I years.”
  • The U.S. finalized the national DST schedule in the 1960s.

• Current Rationale:

  • Today DST’s benefits are debatable. Initially thought to save energy, modern research finds any savings are minimal to nonexistent.
    • Michelle Deng [05:20]:
      “One report from 2008 found we save half a percent of electricity per day…other studies find it doesn’t save energy at all.”
  • Economic arguments (e.g., retail and candy industries like more evening light) have promoted DST, but evidence is mixed about overall economic benefit.

2. Negative Impacts of the Clock Switch: Wildlife and Car Accidents

[06:26 – 13:52]

• Human-Deer Collisions Surge After Fall Switch:

  • Laura Prue, wildlife ecologist, studied deer-vehicle collisions across 23 states and found:
    • 2 million+ deer are hit in the U.S. yearly, mostly at dawn/dusk (“crepuscular” animal activity).
    • After “falling back” to Standard Time, when evening commutes occur in darker conditions, there is a 16% spike in deer collisions in the week after the switch.
      • Laura Prue [11:07]:
        “The switch in the fall led to a 16% increase in collisions. Just comparing the week before the switch to the week after.”

• Public Safety & Economic Costs:

  • These accidents aren’t just tragic for deer: ~60,000 human injuries and over 400 deaths per year in the US are due to such collisions.
  • Permanent DST could prevent 36,000 deer accidents, 2,000 injuries, and 33 deaths annually, saving ~$1.2 billion.
    • Michelle Deng [12:17]:
      “Having permanent daylight saving time could prevent over 36,000 deer car accidents a year across the US … 2,000 fewer injuries and 33 fewer deaths.”

• Other Species & Crime:

  • The collision problem extends to koalas in Australia.
  • Violent crime decreases with more evening light (robberies down 27% during DST).
    • Michelle Deng [13:31]:
      “There was one study that found … robberies went down by 27% when you compare daylight saving time to standard time.”

• Conclusion from This Data:

  • Strong evidence emerges for keeping DST all year, preventing accidents and crime.

3. The Circadian Clock, Sleep Science, and Standard Time

[17:12 – 25:53]

• Spring Forward, Heart Attacks, and Sleep Disruption:

  • The “spring forward” switch is linked to sleep loss, short-term cognitive impact, and possibly a spike in heart attacks and strokes (although new evidence is less conclusive).
    • Michelle Deng [18:13]:
      “The risk for heart attack and stroke goes up in the first two days.”
    • Jamie Zeitzer [18:15]:
      “That’s how fragile and vulnerable your body is to even just the smallest perturbation of sleep.”

• Circadian Rhythm Deep Dive (with Jamie Zeitzer, Stanford sleep scientist):

  • Early-morning light exposure synchronizes the body’s “internal clocks” in various organs, vital for metabolism, hormonal cycles, and general health.
    • Jamie Zeitzer [18:56]:
      “Bright sunshine closer to when you wake up is, in theory, going to strengthen your circadian clock…”
  • Regularity is key: erratic cycles (such as clock changes) weaken this internal synchronization and can negatively impact health (seen clearly in shift workers).
    • Jamie Zeitzer [21:40]:
      “If you have an erratic sleep-wake cycle…it translates to an erratic light-dark cycle, then you get a weaker clock.”

• Is Permanent Standard Time Healthier?

  • Standard Time best matches “solar time” and natural light exposure, potentially better aligning our circadian rhythms.
  • Sleep science and health organizations (American Academy of Sleep Medicine, Sleep Research Society) advocate for permanent Standard Time.
    • Michelle Deng [25:03]:
      “The American Academy of Sleep Medicine…all say we should be on permanent standard time.”

• But Where’s the Data?

  • Jamie Zeitzer critiques the lack of hard evidence.

    • Jamie Zeitzer [25:43]:
      “That’s what everyone’s been saying…‘according to the theory.’ Well, how about some data?”

  • He runs new studies, modeling health “burden” under three scenarios: current switching, permanent DST, and permanent Standard Time.

    • FINDINGS:
      • Both forms of permanent time are healthier than clock switches.
      • Of the two, permanent Standard Time results in slightly better outcomes for obesity and stroke prevention:
        • Preventing 2 million cases of obesity and 300,000 strokes if the country switches to permanent Standard Time.
          • Michelle Deng [28:54]:
            “We could potentially prevent obesity in over 2 million people… and prevent strokes in 300,000 people.”

4. The Messy Middle: Science, Policy, and Lived Reality

[29:55 – 32:41]

• No Simple Answer:

  • Everyone agrees clock changes are the worst option.
  • There is no clear consensus or “slam dunk” scientific answer about which form of permanent time is best for everyone.
    • Michelle Deng [30:01]:
      “It’s kind of funny…I thought there’d be a clearer answer here, but it’s messier than I thought.”

• Public Opinion Is Split:

  • Polls show US citizens are nearly evenly divided between permanent DST and Standard Time.

• Logistical/Nuanced Factors:

  • A universal solution is elusive—different locations within time zones may experience very late sunrises in winter under permanent DST.

  • A 30-minute compromise has been suggested but could introduce logistical headaches.

    • Meryl Horne [30:47]:
      “Can we just, like, split down the middle? … What if we did like 30 minutes?”
    • Michelle Deng [31:00]:
      “Some scientists have actually brought this idea up too…But…could you imagine the logistics of being a half hour offset from other countries…”

• Host’s Opinion and the Case for Caution:

  • Michelle Deng leans toward maintaining the status quo until the science is clearer.
    • Michelle Deng [32:07]:
      “I think controversial take, but I think we should stick with what we have now until the science is super clear.”

5. Practical Advice for Dealing with the Switch

[32:48 – 33:26]

• To blunt the negative effects of the clock change, Michelle recommends adjusting your sleep by small increments the week before:
  • Michelle Deng [33:09]:
    “Adjust your sleep time by 15 minutes a day the week before the actual switch…Basically, ease into the switches so it’s not a whiplash for your body.”
  • Meryl Horne [33:09]:
    “Seems kind of annoying, to be honest…”

Notable Quotes & Memorable Moments

• On the Reality Behind DST’s Origins:

  • Michelle Deng [04:19]: “Interestingly, it has nothing to do with the farmers, but it actually started as a government project to save energy…”

• On the Dangers of Deer Collisions:

  • Laura Prue [11:07]: “That switch in the fall led to a 16% increase in collisions, just comparing the week before the switch to the week after.”
  • Michelle Deng [12:17]: “Permanent Daylight Saving Time could prevent over 36,000 deer car accidents a year across the U.S. … 2,000 fewer injuries and 33 fewer deaths.”

• On Sleep & Circadian Clocks:

  • Jamie Zeitzer [18:56]: “That bright sunshine closer to when you wake up is in theory going to strengthen your circadian clock.”
  • Jamie Zeitzer [20:24]: “You can kind of think of [the central circadian clock] like a conductor of an orchestra.”

• On the Lack of Concrete Data:

  • Jamie Zeitzer [25:43]: “That’s what everyone’s been saying. Oh, according to the theory. Well, how about some data? This is what I’ve been saying for years is I’d like to see some data. And no one ever shows any data.”

• On the Bottom Line:

  • Michelle Deng [30:01]: “It’s kind of funny. I thought there’d be a clearer answer here, but it’s messier than I thought.”
  • Michelle Deng [32:07]: “I think…we should stick with what we have now until the science is super clear.”

Timestamps for Key Segments

• 00:00–03:21 — Introduction: The heated debate over DST and the science behind it
• 03:21–06:25 — Origins and economic/cultural arguments for DST
• 06:26–13:52 — Car accidents, crime, and animal welfare: Harmful effects of the fall time switch and arguments for permanent DST
• 17:12–25:53 — Sleep science, circadian rhythm, permanence of Standard Time, and health impacts
• 25:53–30:01 — New research: Modeling health outcomes of switching vs. permanent time; which is actually healthier?
• 30:01–32:41 — Public opinion split, logistical/equity issues, practical uncertainty
• 32:48–33:26 — How to make the transition easier each year

Final Thoughts

This Science Vs episode highlights that:

• Clock switches are the most harmful policy: They’re associated with accidents, disrupted sleep, and potential health impacts.
• Permanent DST and Standard Time are both better than switching, but each has unique pros and cons, and science isn’t yet a “slam dunk” for either.
• Current science slightly favors permanent Standard Time for metabolic and cardiovascular health, but daylight in the evening offers measurable public safety and economic benefits.
• Public opinion and practicality are split; geographical differences complicate a “one-size-fits-all” solution.
• Practical tip: Prepare your body for the switch by gradually shifting your sleep schedule.

In short: The science points strongly toward abolishing the twice-yearly clock change, but which “permanent” time to pick is still up for debate.