How Time Zones and Daylight Saving Began

Before the late 1800s, communities kept their own local "solar time," set by the sun's position at noon. That worked fine until railroads needed synchronized schedules. In 1884, U.S. railroads created the four time zones we still use today, and the International Meridian Conference established a worldwide time standard the same year. Standard Time became U.S. law in 1918.

Daylight Saving Time has a separate origin: Germany introduced it in 1916 during World War I as a fuel-saving measure, and the U.S. followed in 1918 for the same reason — though it was repealed just a year later. The Uniform Time Act of 1966 eventually put the whole country on DST each summer, with states opting in gradually starting in 1967.

The 1970s Experiment That Failed

This isn't the first time year-round DST has been put into practice. During the 1973–74 energy crisis, Congress enacted permanent Daylight Saving Time nationwide. It lasted only ten months before public backlash, largely over dark winter mornings, forced a repeal. It's the same policy now back on the table.

DST Doesn't Actually Save Energy

The original justification for DST was energy conservation. Decades of research have since debunked that idea: DST has been shown to increase energy use by up to 4% compared to Standard Time, not decrease it. Energy savings simply isn't a valid argument for either side of this debate.

Safety Cuts Both Ways

Supporters of permanent DST often argue that more evening light means safer commutes home. That logic works in both directions, however — more morning light would just as easily reduce accidents and improve visibility for the school and work commute at the start of the day. Under permanent DST, almost everywhere in the country, students would be waiting at bus stops and commuters would be driving to work in pitch darkness, until 8:00 or 9:30 a.m. depending on location.

Why Morning Light Matters So Much

This is where the health case for Standard Time comes in. Our bodies run on a roughly 24-hour internal clock, the circadian rhythm, which governs sleep, hormones, metabolism, and immune function. That clock is set primarily by light, especially light in the early morning.

When we get bright light shortly after waking, it signals the brain that it's time to be alert. Research shows early morning sunlight helps align the circadian clock and supports healthier sleep timing and quality. Permanent DST delays that morning light exposure, especially in winter, which pushes the body clock later and may make both falling asleep and waking up harder.

Stanford sleep neurologist Dr. Logan D. Schneider has explained that Daylight Saving Time denies us the morning light our bodies need to wake up, while also delaying the evening darkness cues that signal it's time to rest, widening the gap between our biological clocks and our social schedules.

Social Jet Lag and Our Health

That mismatch between our internal clock and our social schedule has a name: social jet lag. It's linked to fatigue, poorer sleep, and higher risk of obesity, cardiovascular problems, and mood disorders. Permanent DST would effectively lock a mild form of this misalignment into place for millions of people, especially during winter months.

This is why the American Academy of Sleep Medicine, backed by more than 20 medical and scientific organizations,  and the American Medical Association have both formally called for eliminating seasonal clock changes in favor of permanent Standard Time, not permanent DST. Their reasoning: Standard Time keeps clock time closer to the sun's actual position, delivers earlier morning light, and minimizes social jet lag.

Sleep and Brain Health

Good sleep is one of the most powerful things we can do for our brain. During sleep, the brain clears out toxins and strengthens memory, a process that's disrupted when sleep is cut short. Most adults need 7 to 9 hours a night, and going to bed earlier helps even more: the body produces roughly five times more growth hormone between 10 p.m. and 5 a.m. than between midnight and 9 a.m.

The Bottom Line

Nearly everyone agrees the twice-yearly clock switch should end. Notably, many House members voted in favor of H.R. 139 for that reason alone — to stop the biannual change — not because they specifically preferred DST over Standard Time. That means the real decision, on which permanent time supports us best, is still ahead of us. The evidence points to Standard Time as the option better aligned with human biology, sleep, and long-term brain health. And although I do like it being light later in the evening when we are on DST, I prefer the early morning sunrise in the winter much more!

Take action: Decide which matters more to you — and let your legislators know where you stand on ending the clock change for good.

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