Original image

Blame Leap Year on Mismatched Solar, Lunar, and Seasonal Cycles

Original image

It’s hard to think of anything as complex, and yet as humdrum, as the calendar. These days, clocks and calendars are so ubiquitous—the screen you’re looking at right now can instantly tell you the time and date—that we’re blissfully unaware of the centuries-old intellectual struggle involved in their creation. What better day than February 29—a day that comes only once every four years—to reflect on the story behind our seemingly esoteric method of counting the days of the year.


The complexity of our timekeeping systems isn’t really humanity’s fault. If you’re looking for a scapegoat, I’d blame the solar system. The urge to keep track of time is probably as old as our species, and the most obvious signs of time’s passage are the cycles we observe in nature, especially the regularities we see in the night sky.

Most obvious are the day (measured by the rising or setting of the Sun); the month (measured by tracking the phases of the Moon); and the year (the annual cycle of the seasons). But timekeeping soon gets complicated, because none of these cycles fit neatly into one another: The lunar month is about 29.5 days long (actually 29.5306); the average year as defined by the seasons—also known as the “solar” or “tropical” year—is about 365.25 days long (actually a smidgeon less, at 365.2422 days). And the month refuses to fit neatly into the year, too, for that matter (there are more than 12, but less than 13, lunar cycles in a year). Over the centuries, different civilizations tried every possible trick to try to reconcile these incongruent cycles.

It would have been nice if there were 360 days in a year: The math would be wonderfully simple, since 360 can be divided by 2, 3, 4, 5, 6, 8, 9, 10, and—well, I won’t list them all, but 360 has 22 divisors in all (not counting 1 and 360). But no such luck; the year actually has a bit more than 365 days.


The ancient Egyptians had a fairly elegant solution: Use a 360-day calendar, with 12 months of 30 days each, and then enjoy five days of feasts and celebrations at the end of each year. But it still wasn’t perfect: The resulting year of 365 days is still about a quarter-day short of the true solar year.

The Egyptians recognized this discrepancy early on, and realized that adding an extra day every four years would bring the average length of the year to within just a few minutes of the true solar (tropical) year. It wasn’t until 238 BCE, however, that the Egyptian king Ptolemy III pushed for the adoption of a leap-year system. The Romans—whose empire would eventually encompass Egypt—tried a variety of calendar systems, eventually adopting the now-familiar leap year system, in which every fourth year has 366 days, instead of the usual 365. They’re also responsible for the peculiar lengths of the months. Initially, the idea was to have alternating 30-day and 31-day months, but successive rulers fiddled with those lengths. (For example: July, named for Julius Caesar, had 31 days; naturally, his successor, Augustus, demanded that August must have 31 also—the extra day being taken away from lowly February.)

The Roman calendar wasn’t perfect. Its average year of 365.25 days was just slightly shorter—by about 11 minutes—than the true solar year. By the time of Pope Gregory XIII, in the late 1500s, that discrepancy added up to 10 full days. Springtime holidays like Easter were drifting awkwardly into summer. Gregory convened a council of mathematicians and astronomers, who eventually found a way to make the average year just slightly longer: In the old system, “century years” like 1500, 1600, and 1700 would be leap years because they’re divisible by 4; under the new plan, only those century years divisible by 400 (such as 1600 and 2000) would be leap years.

The proposed reform was adopted in 1582—at which point 10 days were dropped from the calendar to let it “synch up” with the seasons (and so October 4, 1582, was followed by October 15). Some people were distressed at what seemed to be “lost” time. Merchants puzzled over the calculation of profits and losses; bankers were befuddled by interest rates.


While Catholic countries quickly adopted the Gregorian calendar, Protestant countries held off. In Britain, the new calendar wasn’t adopted until 1752—at which point 11 days had to be dropped from the year, in order to “catch up.” Protests broke out in London and Bristol, with workers shouting, “Give us back our 11 days!” Interestingly, such tensions have not entirely disappeared; as The Telegraph points out, some people resent having to work an extra day for no pay in leap years.

Leap years, which have been a part of our timekeeping system for more than 2000 years, barely warrant notice these days— although today’s Google Doodle serves as a cute reminder. Of course, if you’re one of the 4 million or so living leap day babies, known as “leaplings” or “leapers,” you’re likely hyper-aware of leap years. (Calculating the number of people with a February 29 birthday is tricky, by the way: The fraction of babies born on February 29 isn’t 1 in 365, but rather, about one in 1460, since February 29 occurs only once every four years—or, to be precise, 97 times every 400 years.) Famous leap-babies include motivational speaker Tony Robbins, rapper Ja Rule, and the 16th-century pope Paul III. Intriguingly, two major events—the Summer Olympics and U.S. national elections—are always held in leap years.

Dan Falk (@danfalk) is a science journalist based in Toronto. He explored time and timekeeping in his 2008 book, In Search of Time.

Original image
A Brief History of Time
Original image

You may have heard that time is a social construct, but that doesn’t stop it from having consequences in the real world. If you show up to a party 10 minutes before it’s scheduled to start, you’ll likely be the first one there, and if you arrive to an interview 10 minutes late, you likely won’t get the job. But how did humanity agree on when and how to observe certain times of day?

In their new video, the It’s Okay to Be Smart team explains how humans “invented” the modern concept of time. The increments we use to measure time, like seconds, minutes, and hours, come from the ancient civilizations of the Egyptians and the Babylonians. Early clocks, like sundials and water clocks, were pretty crude, so people couldn’t pinpoint a time like noon down to the second even if they wanted to. But as clocks became more accurate, the problem wasn’t being unable to tell time accurately, but deciding which clocks qualified as “accurate” in the first place.

In 1884, President Chester A. Arthur organized the International Meridian Conference with the intention of deciding on a uniform definition of time to be followed around the world. The attendees ended up choosing the meridian running through Greenwich, England as the official Prime Meridian, and all clocks would be measured against the clock in the town’s observatory. Greenwich Mean Time is still used as the standard world time today.

Check out the full story below.

[h/t It’s Okay to Be Smart]

Original image
Jonathan Daniel/Getty Images
Big Questions
Why Do Baseball Managers Wear Uniforms?
Original image
Jonathan Daniel/Getty Images

Basketball and hockey coaches wear business suits on the sidelines. Football coaches wear team-branded shirts and jackets and often ill-fitting pleated khakis. Why are baseball managers the only guys who wear the same outfit as their players?

According to John Thorn, the official historian of Major League Baseball since 2011, it goes back to the earliest days of the game. Back then, the person known as the manager was the business manager: the guy who kept the books in order and the road trips on schedule. Meanwhile, the guy we call the manager today, the one who arranges the roster and decides when to pull a pitcher, was known as the captain. In addition to managing the team on the field, he was usually also on the team as a player. For many years, the “manager” wore a player’s uniform simply because he was a player. There were also a few captains who didn’t play for the team and stuck to making decisions in the dugout, and they usually wore suits.

With the passing of time, it became less common for the captain to play, and on most teams they took on strictly managerial roles. Instead of suits proliferating throughout America’s dugouts, though, non-playing captains largely hung on to the tradition of wearing a player's uniform. By the early to mid 20th century, wearing the uniform was the norm for managers, with a few notable exceptions. The Philadelphia Athletics’s Connie Mack and the Brooklyn Dodgers’s Burt Shotton continued to wear suits and ties to games long after it fell out of favor (though Shotton sometimes liked to layer a team jacket on top of his street clothes). Once those two retired, it’s been uniforms as far as the eye can see.

The adherence to the uniform among managers in the second half of the 20th century leads some people to think that MLB mandates it, but a look through the official major league rules [PDF] doesn’t turn up much on a manager’s dress. Rule 1.11(a) (1) says that “All players on a team shall wear uniforms identical in color, trim and style, and all players’ uniforms shall include minimal six-inch numbers on their backs" and rule 2.00 states that a coach is a "team member in uniform appointed by the manager to perform such duties as the manager may designate, such as but not limited to acting as base coach."

While Rule 2.00 gives a rundown of the manager’s role and some rules that apply to them, it doesn’t specify that they’re uniformed. Further down, Rule 3.15 says that "No person shall be allowed on the playing field during a game except players and coaches in uniform, managers, news photographers authorized by the home team, umpires, officers of the law in uniform and watchmen or other employees of the home club." Again, nothing about the managers being uniformed.

All that said, Rule 2.00 defines the bench or dugout as “the seating facilities reserved for players, substitutes and other team members in uniform when they are not actively engaged on the playing field," and makes no exceptions for managers or anyone else. While the managers’ duds are never addressed anywhere else, this definition does seem to necessitate, in a roundabout way, that managers wear a uniform—at least if they want to have access to the dugout. And, really, where else would they sit?

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at


More from mental floss studios