People in the United States will feel a bit more refreshed on November 3 as daylight saving time 2019 comes to an end. The clocks fall back at 2 a.m. ET on Sunday, ushering in three months of getting up in the dark until the winter solstice welcomes back the sun on December 21.

You’ve probably heard that Ben Franklin kind of proposed daylight saving time (also erroneously called daylight savings time) centuries before it was implemented, and that the twice-yearly switch was initially adopted to save us money on energy needs.

But if you dig deeper, you’ll find out that the daylight-hoarding tradition—which was adopted in the United States just over a hundred years ago—has an even more colorful history. Around the world, daylight saving time has been affecting international relations, creating nested time zones, and potentially influencing your health. (See where the movement to abolish daylight saving time is gaining steam.)

Here are a few of the lesser-known facts about daylight saving time.

Daylight Saving Time 101 Learn about how daylight saving time has both benefits and negative consequences.



Thrift wasn’t the only reason for saving daylight

In 1895, George Hudson, an entomologist from New Zealand, came up with the modern concept of daylight saving time. He proposed a two-hour time shift so he’d have more after-work hours of sunshine to go bug hunting in the summer.

Seven years later, British builder William Willett (the great-great grandfather of Coldplay frontman Chris Martin) independently hit on the idea while out horseback riding. He proposed it to England’s Parliament as a way to prevent the nation from wasting daylight. His idea was championed by Winston Churchill and Sir Arthur Conan Doyle—but was initially rejected by the British government. Willett kept arguing for the concept up until his death in 1915.

In 1916, two years into World War I, the German government started brainstorming ways to save energy.

“They remembered Willett’s idea of moving the clock forward and thus having more daylight during working hours,” explains David Prerau, author of Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time. “While the British were talking about it year after year, the Germans decided to do it more or less by fiat.”

Soon, England and almost every other country that fought in World War I followed suit. So did the United States: On March 9, 1918, Congress enacted its first daylight saving law—and it was a two-fer: In addition to saving daylight, the Standard Time Act defined time zones in the U.S.

In those days, coal power was king, so people really did save energy (and thus contribute to the war effort) by changing their clocks.

Daylight saving time is all over the map

Today, the idea of springing forward and falling back is a bit more controversial, in part because it no longer really saves energy. But when you hear from a time-change skeptic, consider the source and where they live. If they’re from a more northerly place, they may be inclined to like saving daylight more.

It’s a matter of geography. The further you travel from the Equator, the more drastic the seasons will be. That’s because Earth is tilted on its axis with respect to the sun, so the top and bottom portions of the globe receive more or less sunlight at different times of the year, making the loss of daylight hours more pronounced.

In the middle portions of the planet, the amount of sun is about the same all year ‘round. As a result, the seasons are milder and there’s less of a need to make adjustments to maximize daylight. Just look at a map of the countries that use daylight saving time today to see which regions really find the shift worthwhile.

Arizona’s relationship to daylight saving time is … complicated

Daylight saving time indifference causes one U.S. state—Hawaii—to brush off the time change entirely. Arizona, where scorching temperatures often make night the only bearable time to be outside, also said no to moving its clocks around, because its residents preferred to savor the cool nighttime hours.

“In the summer, everybody loves to have an extra hour of daylight in the evening so they can stay out another hour,” Prerau explains. In Arizona, it’s just the opposite, he says. “They don’t want more sunlight, they want less.”

However, the daylight saving situation within Arizona is even more confusing. While most of the state ignores daylight saving time, the Navajo Nation, which covers part of northeastern Arizona, observes it. Meanwhile, the Hopi Reservation, which is surrounded entirely by the Navajo Nation, does not. And within the Hopi Reservation sits a small slice of the Navajo Nation that, you guessed it, does observe daylight saving time.

Long story short: If you’re driving through northeastern Arizona, you might want to ask for the time instead of relying on your own watch.

And on March 5, the Florida State Senate passed the Sunshine Protection Act, which would make daylight saving time always on in the state. Opting in year-round will require approval from Congress, but if it’s granted, Floridians will join the ranks of those who no longer need to worry about the biannual time warp.

Daylight saving time can have deadly consequences

Well, kind of. The transition to and from daylight saving time has been linked to higher heart attack risk, more car accident fatalities, and other bad outcomes. But Prerau points out that those effects—thought to be due to sleep deprivation and circadian rhythm changes—are just temporary.

“It’s very important for people to understand the difference between short-term, transitional effects and long-term benefits,” he says. “You’re talking about an eight-month benefit versus a one- or two-day negative.”