Daylight saving time, explained

Why people hated permanent daylight saving time in 1974

Messing with the amount of daylight each day has consequences, as America found out in 1974 when it first passed all-year daylight saving time. See why it was revoked less than a year later.

Daylight Saving Time is linked to a rise in heart attacks and strokes

Losing an hour of sleep with seasonal time changes is not good for our health and it’s linked to risks for the first couple days of Daylight Saving Time, including a short-term rise in heart attacks and strokes. Scientists theorize these elevated risks are linked to the disruption to the body’s circadian rhythm.

The Benjamin Franklin letter that anticipated daylight saving time

Benjamin Franklin did not invent daylight saving time. But while living in Paris, he did pen a satirical letter to Parisians suggesting they could save money on lamp oil by changing their sleep schedules. Read it in full here.

The science of springtime, 101

Dive into the basics on springtime including the astronomy that brings it about, natural signs of spring's arrival, and some of the cultural approaches to the season.

The world's quirkiest time zones

In contrast to telling time by physical signs like the sun or stars, cultural time relies on political agreement and standards. The convention of time zones arose due to transportation and communication advancements, and while many work just fine, some are pretty wild. Chief among those is the time zone of the uninhabited Baker and Howland Islands in the central Pacific, which results in a technical 26-hour day.

There is a template for how to live a better, healthier day, and it includes a digital sunset

Science suggests that early-morning exercise, later-morning peak work or social time, consistent exercise, and a "digital sunset"—starting to turn down the lights in the evening and avoid screens—are important for circadian health.

The world's different calendars, explained

The calendar we use to mark the days, months, and year can feel set in stone, but the history of calendars shows these organization systems can and do change. Parse the fascinating, complex details of the Gregorian, Julian, Chinese, Hebrew, and many more calendars in this comprehensive, well-executed explainer video.

The difference between solstice and equinox, explained

A solstice marks the extremes in the amount of day or night, while the equinoxes come on days with a balance between the two. Learn why with this brief video.

Visualize your city’s annual daylight map

Type in your town or region and see sunrise and sunset for each day of the year. A separate view shows the number of hours of day versus night for each day. Search a city far north like Oslo, Norway, and compare its graphs to one near the equator (like Singapore).

Why don't humans hibernate?

Hibernation is a superpower in the animal world that allows certain species to time travel from difficult times to abundance. This essay in Aeon explains this helpful natural process and why humanity's technological advancements may have hindered our ability to participate in the practice. Learn about the rising interest in human hibernation as a result of modern adversity, and if it could potentially become a reality.

Norman Rosenthal’s struggle with SAD inspired him to understand it

The South African doctor migrated to New York City in the 1970s. During his first winter there, he noticed the shorter days had a significant impact on his mood compared to those in his hometown of Johannesburg, South Africa, which is much closer to the equator. After three years of this seasonal mood shift, he decided to focus his studies. Hear him speak in this quick narration.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Time dilation explains that movement through space affects the passage of time

According to special relativity, everything in the universe moves through space-time at the speed of light. Just as turning from north to northwest on a road reduces one's northward motion, moving through space leaves less of this speed to move through time, causing an object to age more slowly.

Each design detail on the US $1 bill has significance

The eye in the triangle floating above the pyramid, for instance, is “the Eye of Providence watching over and ensuring the endurance of the structure of the American government.” This article details every design choice’s significance on the dollar—and a few conspiracies around these choices as well.

Demystifying sunscreen

Sunscreen is helpful all year round. Experts argue a minimum level of protection is SPF 30. There are two kinds of sunscreen: mineral (a physical barrier) and chemical (absorbs UV light). No new sunscreen ingredients have been approved in the US in decades, so foreign products are common.

Illinois rolled back its happy hour legislation in 2015, opting to cap reduced-price drink sales at 15 hours per week and prohibit them after 10 pm instead

In this episode of the podcast “The Right to Drink,” alcohol expert and host Jarrett Dieterle explains why some states allow happy hour while others don’t. The host also dives into the fight to change happy hour legislation across the US.

What the stars once meant to ordinary people

The stars were a crucial aid for ordinary human beings in premodern societies, acting as regular timekeeping phenomena and celestial navigators. Today, light pollution and modern technology have rendered the stars a mere aesthetic delight for most of us, but their significance in history remains. Watch this brief video to learn how premodern humans used the stars for navigation, mathematics, and more.

Learn about the history of the Monroe Doctrine

CBS Sunday Morning explores the origins of the Monroe Doctrine, tracing how a 19th-century warning against European intervention shaped US foreign policy and influenced America’s role in the Western Hemisphere for generations.

A brief explainer on food expiration dates and what they really mean

Roughly 20% of food items in the US are thrown out because consumers don't understand how to interpret expiration labels. Over time, when supermarkets began carrying processed foods, grocers use packaging codes to track how long foods had been on...

Hear about the 250-year history of the United States Postal Service, complete with some of its strangest deliveries, important innovations, and the figures that made it an American institution.

Watch a breakdown of tax breaks most Americans don't know about

Programs like healthcare savings accounts or flexible spending accounts are tax-free accounts that are designed to help lower healthcare costs. However, many Americans don't use them and don't understand how they work.

Dark matter and dark energy, explained

What is dark energy? What is dark matter? Well, if we knew exactly, we would have a Nobel prize—we know that they exist, though. Scientists have theorized that the former may be a property of three-dimensional space itself, while the latter could be exotic particles that interact with almost nothing. This video from Kurzgesagt explains what we know and what we don't.

Rare chance for US states to see Northern Lights

A solar storm in July 2023 offered people in 17 American states, as well as Canada, an unusual chance to witness the Northern Lights, or aurora borealis. The 11-year solar cycle, reaching its peak in 2024, made the lights visible in places further south than usual. Read up on the announcement from the Geophysical Institute at the University of Alaska at Fairbanks here.

The holiday has evolved alongside its participants' cultural identities

The Day of the Dead blends various traditions, including Aztec myth, Mexican heritage and Chicano identity. That makes for a complex and evolving holiday. This conversation between Cynthia Vidaurri, a Smithsonian folklorist, and Lalo Alcaraz, a cultural consultant for “Coco,” analyzes how the varied influences have created the modern holiday.

Larger shares of solar power generation produce larger energy demand curves

Because solar energy is only available during daylight hours, transitioning an electric grid to solar requires significant ramp-ups and ramp-downs of other energy sources during mornings and evenings to compensate. Widespread adoption of affordable energy storage solutions can soften these curves.

How Americans have voted throughout history

From shouting candidates’ names, to hanging chads to electronic scanning, the nature of voting has a long, sometimes bumpy history in the United States. See descriptions and images in chronological order with this digestible timeline.

Why Hawaiians live longer

Hawaii has the longest life expectancy at birth out of all 50 states, according to the US Centers for Disease Control and Prevention. Key factors include strong healthcare, lots of sunlight, and active lifestyles.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

The idea for the Federal Reserve was conceived in secret in 1910—with bankers donning duck hunt gear for disguise while traveling to a remote country club on Georgia's Jekyll Island

20,000 letters to the advice columnist 'Dear Abby' provide insight into prevailing sex, religion, and LGBTQ fears, anxieties, and concerns from the 1950s onward.

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

After the Boston Tea Party, colonists switched to coffee, which became the main morning drink for revolutionaries.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

Up to a million Girl Scouts sell about 200 million cookie boxes every spring, generating $800 million, largely because refusing a child is frowned upon

Telehealth demand for GLP-1s for weight loss is booming as consumers seek easier access.

Doctors differentiate between a phobia and fear by asking patients whether their fear interferes with their day-to-day activities.

Use this tool to calculate the dollar value of your parental mental load, from meal planning to coordinating after-school care, then see resources that help generate solutions.

Dorothy's famous entrance into Oz in 'The Wizard of Oz' relied on analog tricks, including a body double and sepia-toned paint, as much as it did on technology

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

Netflix profits when you're not watching, and its movies are designed that way—read a detail-rich critical essay exposing lesser-known Netflix takes

70 years ago today, city officials in Santa Cruz, California, banned rock 'n' roll to protect its youth from corruption after witnessing a 'provocative' concert the night before.