The world's different calendars, explained

How people imagine a calendar year

It turns out everybody imagines the abstract calendar year in a simple, concrete way, though there are surprising differences between the exact model and shape of each image. Dive into one writer's collection of tens of thousands of questionnaire responses showing the fascinating consistency and divergence of how people visualize time.

How the months of the year got named

Curious about how the months got their names? This article from The Old Farmer's Almanac explores the origins of today’s Gregorian calendar. Based on the ancient Roman lunar calendar, the months were named after Roman gods until winter when the names changed to numerical titles. Read along to learn the significance and intentions behind labeling each lunar cycle.

China has used several different calendars because of changes in government structure

For many centuries, during which China was an imperial nation, the lunar/lunisolar calendar (aka the “rural calendar”) was the basis for organizing the year. Several attempts were made over the decades to switch to the Gregorian calendar—which begins Jan. 1—but it wasn’t until the People’s Republic of China was founded in 1949 that it stuck.

Why we have different seasons

Visualize just how exactly seasons come to be with this animation of the earth in relation to the sun, and see how earth's tilt determines our seasons.

The calendars of the 'Lord of the Rings'

JRR Tolkien's epic fantasy trilogy "The Lord of the Rings" is a seminal work in the history of literature partly due to its creator's obsessive focus on systematic detail—including the calendars used in the world. Take a fantastic dive into the minutiae of Tolkien's creation by learning the different approaches to time organization in the Shire or Rivendell with this dense, comprehensive resource based on Tolkien's appendices.

A 2,000-year history of alarm clocks

Clocks have revolutionized the way we live, structuring our days into abstract, regular units and providing quantification for those who are chronically late. The alarm clock was the next obvious step: clocks which not only tell you the time but...

How the moon moves, an interactive lesson

How exactly does the moon move, and why does it move that way? In this ridiculously comprehensive interactive explainer, you can conduct experiments to see how the moon rotates and as it moves around the Earth, while learning how gravity works by controlling the path and speed of different objects. Dive into this beautiful, simple explainer to learn the basics on gravity and the moon.

Explained: The Year of the Rabbit

One of the world's largest holidays, this visual guide will help you welcome the Year of the Rabbit and celebrate the new lunar year.

An interactive timeline of history, from beginning to middle

The history of humanity is a long, winding road, and the history of everything else is even more complex and interwoven. This interactive timeline takes users through the history of the world and includes links to related videos, blurbs, and events. Each event in history is represented by a dot, providing users with a glittering horizon filled with moments of intrigue and impact.

Why are all maps of the world wrong?

This 5-minute video explains why all maps to date are verifiably wrong. While globes can provide an accurate map and scale of the various continents, flattening that sphere has historically meant something will be distorted, whether land, sea, or...

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.

Hear how Advent calendars have become a pricy branding tool

Advent calendars have shifted into a high-margin branding vehicle, with retailers prioritizing elaborate design and reusable packaging. This episode questions whether premium calendars—despite their rising prices, environmental concerns, and flashy marketing—actually deliver products worth the cost.

Five charts that changed the world

Data visualization helps us understand the world, providing a powerful way to communicate complicated information in a quick and efficient way. There are many different ways to create graphs, and these five examples—the pie chart, geographic dot...

Hanukkah is one of 8 major Jewish holidays

This calendar, maintained by the Reform Judaism organization, not only shows when each holiday is to be celebrated in the current year, but also includes short histories and common rituals.

Daylight saving time, explained

Daylight saving time is supposed to help—but does it? Dive into the history, science, and consequences of this biannual aspect of American life (unless you're from Arizona or Hawaii).

The gut microbiome, explained

This video from 1440 takes a high-level look at what populates the gut microbiome, its purpose, how it affects our health, and much more.

How Eastern Orthodox and other Christians celebrate Easter differently

Western churches switched to the Gregorian calendar in 1582, though the Orthodox Church still calculates Easter using the Julian calendar, which runs 13 days behind. Orthodox Easter also must always follow Jewish Passover. The result is two Easters that can fall up to five weeks apart.

Get lost in these historical libraries

The internet has changed a lot about how we learn, explore new ideas, and conduct research, particularly when it comes to the spaces we learn in. While few of us would trade our smartphones for a walk in a historical library, a walk through some of the beautifully designed cathedrals of learning could remind us to put them down sometimes. Explore 10 of the world's magnificent libraries with this quick video survey.

The rise and fall of the Byzantine Empire

A short but informative TED-Ed video summarizing the most important aspects of Byzantine civilization: how it all started, why Constantinople was so special, a few remarkable Byzantine authors (including Princess Anna Comnena, historian of her father’s reign), the Ottoman conquest, and why don’t just call the Byzantines “Romans.”

Inside a congressional office, the scheduler is more powerful than you think

A former congressional scheduler explains that a member's time is the scarcest resource in any Hill office, and controlling the calendar means understanding every competing claim on it, from the legislative team to the member's family. The interview demystifies how a typical House office actually functions, from staff hierarchies to outside resources like the Congressional Research Service.

Explaining the many-worlds interpretation

A mind-bending, jargon-free account of the popular interpretation of quantum mechanics, helping to explain how something can be in two states at once.

How the soccer World Cup works

The World Cup is the biggest game in the world. Watch this video to learn how it works and how it came to be such a massive world event.

See how fireworks are made and which metals are responsible for different colors

This roughly five-minute video breaks down details about how pyrotechnicians make fireworks, including that magnesium is responsible for white fireworks, copper salts for blue, and charcoal for orange.

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...

See how Stonehenge was built

This short animation shows how human beings managed to lug 30-ton stones over miles of prehistoric English countryside and stand them up The Stone Age engineering involved using giant wooden rollers and carving precisely interlocking tongue-and-groove joints to hold the heavy stones in place.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

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

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

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.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

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

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

A century of Billboard issues documenting the evolution of popular music.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions

Watch how algorithms can be designed to train themselves and self-improve without human input, to the point where the optimized code is too complex for programmers to understand.

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.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

Watch this video that uses Lego bricks to explain how venture capital works.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

Meet the 56 signers of the Declaration of Independence—most of whom didn't put pen to paper until August 2, 1776—and see their original signatures.

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects