What is the greatest human discovery or invention of all time? Which idea has most changed the way we understand the universe? Which single concept provided the base pavement for the road to our current way of life? The answer to all three questions is, I think, Time.

Before we landed a spacecraft on Mars, humans needed to predict the seasons. Farmers needed to know when to plant and harvest; religious leaders needed to know when to celebrate holidays and hold festivals. How could this be done? If someone asked you this question on the street tomorrow, would you be able to answer without referring to modern time-keeping devices? I know I wouldn’t. The history of telling time is a fascinating and rich one, and although the inceptive analysis of this problem probably predates recorded history, our story begins in ancient Egypt, in the year 3200 B.C.

The First Calendars:

Five thousand and two hundred years ago, the ancient Egyptians—without any notable zest for mathematics—provided one solution to the problem of Time. They invented a working calendar that solved essentially all the practical needs throughout the land. The calendar, based off the rising and falling of the Nile River (ever wonder where the term ‘Nilometer‘ came from?) was simply a vertical scale on which the flood level was annually marked. The Egyptians somehow figured out that if they added another five days to their system—adding up to a total of 365 days—they could make a useful calendar for the seasons.

The Cairo Nilometer

So powerful was this simple time-log that under it, the entire Nile Valley was united with the Nile Delta into a single kingdom which lasted for three thousand years, until the Age of Cleopatra. So concrete was their system that in the year 46 B.C Julius Caesar used it to create his Julian calendar and in the sixteenth century Copernicus used it to construct his planetary tables. Its only pitfall stems from the observation that a true solar year is not precisely 365 days, and so over the centuries this small discrepancy grows and grows until the original set-up no longer accurately predicts the seasons. However, since this change takes hundreds of years to become noticeable, the ancient Egyptian’s had, for all intents and purposes, invented the first successful calendar. But even in the face of the Nile calendar’s immense accuracy and utility, intermediate civilizations—obstinately blinded by political and religious traditions—refused to use non-lunar calendars.

The Moon as a Natural Clock:

Why is it that all modern religions are imbued with a mythical or metaphysical revelry for the Earth’s moon? And why do they still tightly latch on to their outdated calenders? Ridiculous and primitive as they may seem, we must forgive modern religion for succumbing to, in the words of the historian Daniel J. Boorstin, “the temptations of the moon” (The Discoverers, pg 4).And if you think about it for a moment, it is not hard to see why so many ancient civilizations and modern religions use the moon as a natural clock: it’s 28 day cycle, which eerily lines up with the average woman’s menstrual cycle, displays an obvious kind of rough periodicity. To the ancient eye, what better way to keep time?

The ancient Babylonians, probably in the year 432 B.C (Dictionary of Greek and Roman Biology and Mythology, pg 1069 ), had invented the Metonic Cycle (after the astronomer Meton). The Metonic cycle, a lunar calendar

, consisted of nineteen-years, seven of which were thirteen months long, the rest twelve. To harmonize the calendar with the solar year, the Babylonians had to occasionally insert extra months, a practice called ‘intercalation’. This proved overly complicated for everyday use, and was eventually dropped.

The ancient Greeks also fell victim to the moon’s allure; and due to the nation’s geographic fragmentation, each of Greece’s city-states made its own calendar, each of which required intercalating such that certain seasons fell on politically or religiously important days. This, as you may already be th

inking, utterly defeats the purpose of a calendar—which is “a time scheme to hold people together, to ease the making of common plans” (The Discoverers, pg 6).

The Modern Calendar:

Pope Gregory the XIII

So how did our calendar, the Gregorian calendar, become what it is today? You may remember Pope Gregory XII from your European history course as an accomplice to the brutal Saint Bartholomew’s Day Massacre of anywhere between 5000 to 30,000 Parisian Protestants in 1572. But we must also remember him as an active reformer, and the man directly responsible for creating the calendar by which we live today.

In 1582, he issued a papal ordinance declaring that October 4^th was to be followed by October 15^th. The logic behind his decision was as follows: the vernal equinox must occur, as the solar calendar of seasons mandates, on March 21^st. By removing ten days out of the calendar in 1582, the equinox would happen on the correct date in 1583. The other issue with reforming the Julian calendar was how to avoid the accumulation of minor discrepancies like the ones the ancient Egyptians had seen. The solution is ingenious and simple: omit the leap day from years ending in hundred, unless they are divisible by 400. And voilà, there you have it—two relatively uninvolved changes to the old Julian (and by extension the ancient Egyptian) calendar made the time-system we still abide by today.

It was expected that everyone would immediately adopt this new and approved system, but because of Protestant England and America’s hatred of anything Roman, it was not until 1752 that they were convinced to make the switch from Julian to Gregorian. Benjamin Franklin, with his characteristic wit and brevity, commented on this loss of days in the Poor Richard’s Almanack:

Be not astonished, nor look with scorn, dear reader, at such a deduction of days, nor regret as for the loss of so much time, but take this for your consolation, that your expenses will appear lighter and your mind be more at ease. And what an indulgence is here, for those who love their pillow to lie down in Peace on       the second of this month and not perhaps awake till the morning of the fourteenth.

The Weeks and Days:

Where did the week come from? And why is it seven days long, rather than five or ten? Why does the week even exist? After a little digging, we find that the English word week is derived from the old High German wecha, meaning ‘to change’. In light of this etymological fact, some historians and philosophers argue that the concept of the week—while entirely a human creation with no outside reference point (like the moon or sun)—comes from an innate human desire to replenish the body and mind. As is the case with many historical claims: this postulate is not falsifiable, but nevertheless interesting and worth playing with. We can’t be exactly sure of the week’s origins, but many historians think it may have come from ancient Babylonia and references the Sun, Moon and the five visible planets.  Since the Jews were Babylonian captives during the fifth and sixth century BCE this would explain why Judaism has its seven day Creation story, and why so many subsequent civilizations used (and continue to use) seven day weeks.

Okay then, so we know that the week itself was likely arbitrarily made-up, but what about the days of the week? How they get their names? The answer unveils the quintessentially human impulse to be connected with the cosmos around us: the names of the week are each dedicated to a different planetary body. Sunday is self-explanatory; Monday is moon-day; Tuesdays (Mars) is Martes in Spanish; Wednesday (Mercury) is Mercredi in French, Thursday (Jupiter) is Giovedi in Italian, Friday is Viernes (Venus) in Spanish, and Saturday is, aptly enough, Saturn’s Day.

If you were wondering where the English names for days of the week come from, the answer is that, since English is a Germanic language, some of the original names (related to Roman planetary gods) were swapped with the names of  German gods.  Friday was named after the God of Love, Frigg. Thursday was named after the Norse god Thor, who I’m sure we all have heard of. Wednesday is a play on Woden’s day, Woden was a god similar in some ways to Mercury. And finally, the Germanic God of War was Tiu, as in Tui’s-Day.

Conclusion:

There are two lessons to take away here.

The first is that there exist many different solutions to any particular problem, and it is the hallmark of humanity’s genius to converge on the best or most efficient one as the generations fly by.

The second is that even the most banal constructs have a fascinating history. The interdependence and connectedness of all things past and present provides enough inspiration to write for a lifetime.