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  • Writer's pictureBruce Boyce

Time Marches On

Updated: May 15, 2022

Francois-Joseph Servois's 1813 perpetual calendar

"What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know."

Saint Augustine

From the Neolithic to the modern age, mankind has been obsessed with time. Our primitive hunter-gather ancestors observed the cyclic patterns of the moon and sun. They observed the connections between seasons, migrations of important animals, and the best time to collect seeds or fruits. They developed ways to track the passage of time from marks on sticks or stones to cave paintings to the building of megalithic stone circles.

With the advent of civilization, there came agriculture, cities, government administration, and organized religion. From all this grew a greater need to develop an accurate and standard way of keeping track of time. The earliest calendars appear among the Sumerians. The Sumerians were one of the first civilizations to appear sometime after the sixth millennium BCE along the Tigris and Euphrates Rivers in what is now Iraq. The Sumerian calendar was a lunisolar calendar. That is, it was based both on the cycles of both the moon and the sun.

Sumerian star chart

They divided the year into 12 months each starting with the sighting of the new moon. (Month and moon derive from the same linguistic root.) The months would alternate between 29 and 30 days. A day was divided into six hours of daylight and six hours of the night. Since there was no standard length, the hours of the day changed from season to season. The Sumerians ran into the same problem all lunisolar calendars have. Eventually, the monthly lunar cycle becomes misaligned with the solar cycle. A lunar year is roughly 354 days whereas the solar year is 365. Somewhere along the line, the calendar must be brought in sync with the solar cycle. This is achieved by inserting periodically extra days into the calendar. These are called intercalary days or months. The Sumerians inserted an intercalary month generally every three years. These were done individually by royal decree rather than built into the calendar system itself.

Egyptian calendar, Temple of Kom Ombo

The ancient Egyptians utilized two different calendars. One was a civil calendar and the other was a religious one. The civil calendar was based strictly on the solar year. It had 365 days and was divided into three seasons of 120 days each. These three seasons were further divided into four months of 30 days. The Egyptians added five intercalary days that were not considered a proper part of the year. The actual length of the solar year is 364 1/4 days and so the Egyptian calendar would slip one day every four years. Because of this, the Egyptian months rotated through the year and later on be referred to as the wandering year. There is little evidence that the Egyptians made any overt corrections to account for this misalignment until the Romans took over under Augustus Caesar. The religious calendar was based only on the lunar cycle and there is no indication they tried to synchronize these two calendars. The Aztecs in Mesoamerica used a similar system of having an agricultural calendar based on the solar year and then a lunar calendar for keeping track of religious festivals and rituals.

Aztec sun stone, Mexico City, Mexico

Our modern calendar traces its ancestry back to the Romans. According to the Roman historian Livy, the original Roman calendar was created by the legendary first king of Rome, Romulus. The calendar was divided into ten months starting with March. The winter months, when no one worked the fields, were not counted. The original ten months were Quinctilis, Sextilis, September, October, November, and December. Livy also notes that the second king of Rome, Numa Pompilius, divided the year into twelve months by adding Januarius (January - named after the Roman god Janus) and Februarius (February - after the Latin for purification). At first, each of these months had 28 days making the year 354 days long. Due to superstition, a day was added to January to make the year 355 days. February left with an unlucky even number of days, became the month to perform the Roman rituals of atonement and purification. A fitting way to end the year. The first day of each month was called a kalend - hence our word calendar. (The middle of the month was referred to as the ides.)

Reproduction of the Roman Fasti Antiates Maiores calendar

Like most ancient calendars, the Romans found that there was a discrepancy between the solar year and their calendar year. The college of pontiffs (priests) was in charge of maintaining the calendar. They would insert the necessary intercalary days, but such changes to the calendar were often viewed as being unlucky. There were times the college was hesitant at adding days. More often than not though, changes to the calendar were made for base partisan politics. Days could be added to lengthen one's term in office or days could be taken away to shorten the term of one's political opponent. By the late Roman Republic, the calendar was a mess. At one point, the discrepancy between the calendar and the actual seasons was three months. People were celebrating harvest festivals at the height of the growing season. Then along comes Julius Caesar.

In 46 BCE, Julius Caesar returned to Rome from his stay in Egypt consorting with Cleopatra. Inspired by the Egyptian solar calendar and with the help of astronomers from the city of Alexandria, he introduced a new reformed calendar - what we call the Julian calendar today. In the first year, the missing ninety days were woven back into the calendar. The first of the year shifted to January 1st, and the days of the month were set like they are now. Thirty-one days for January, March, May, July, August, October, and December. Thirty days for April, June, September, and November. Poor February was stuck with 28 days. The result was a year of 365 days and four equal seasons. The winter solstice was determined to be December 25. March 25 was the vernal equinox and September 24 as the autumnal equinox. June 24 became the summer solstice. A leap year was added every four years whereby February 24 would be celebrated twice. When Caesar was assassinated, the month of Quinctilis was changed to Julius ( the month he was born) - July. Later on, Sextilis would be renamed Augustus - August - in honor of Augustus Caesar, the first Roman Emperor.

The Julian calendar would serve as the accepted calendar throughout the West over the next millennia. As precise as it was, no one realized that the Julian year was 11 minutes longer than the actual solar year. Over the course of that millennia, the calendar slowly crept out of sync with the solar cycle. It was not until the 16th century, with greater scientific knowledge and more precise timekeeping instruments, did people realize that the year was nearly ten days out of whack. This spurred Pope Gregory XIII to make adjustments to the Julian calendar in 1582.

He decreed that in 1582, the calendar would skip those ten days and go from October 4th to October 15th. To prevent such a slippage again, it was determined that three leap years would be eliminated every 400 years. A leap day would not be used for years ending in hundreds unless they were divisible by 400. (This happened in the year 2000.) The Gregorian calendar is the calendar we utilize today. England, which hated anything related to the papacy, resisted adopting the new calendar until 1752. That's why if you do genealogy, you often find two dates.

Segment of Chinese calendar, British Museum

The Gregorian calendar has been adopted as the standard civil calendar throughout the world. There are many cultures though - Jewish, Islamic, Asian - that still utilize ancient lunar calendars for religious purposes. Yet as precise as the Gregorian calendar seems to be and how adequately it reconciles the cycles of the moon and the sun, our fascination with time has not ended. Albert Einstein showed us how time is relative and how time is woven into the fabric of space. The Atomic Age has gifted us with more precise timekeeping devices. We haven't been able to travel back in time, but scientists are working to understand how time operates at the subatomic level. In the quantum realm, scientists have conducted experiments that they believe show time moving backward.

Which I suppose leaves us with Saint Augustine's quandary. What is time? I feel as if I know what it is, but I can't really explain it. Which is an interesting dilemma for a historian where time is at the heart of our profession.


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