The Julian Calendar: Technological Breakthrough of the Past

by Kit Hawthorne

We talk a lot about how technology has transformed the modern world, and for good reason. The 20th century saw the rise of automated production, the digital revolution, and global connectivity—and things have only sped up since then. Starting in the 21st century, computational power has doubled approximately every two years, leading to snowballing advances in automation, data analysis, and artificial intelligence.

But a lot of the everyday conventions and devices that we take for granted were huge innovations when they were first introduced (and, of course, provide the foundation for later advancements). Arabic numerals, alphabetic writing, libraries, indexes, concordances, classification systems for living organisms, measurement systems, navigation, cartography, standardized coinage, postal services, mechanical clocks, codified systems of law—these intellectual technologies didn’t just make it easier for people to perform physical tasks. They revolutionized the way people thought. Every one of them has its own complex and fascinating history, often reaching back to the ancient world.

But the intellectual technology that I want to drill down on today is calendars—specifically, the Julian Calendar, which made its first appearance in 45 B.C.

The Tusculum Portrait of Julius Caesar

We deal with calendars in some form or other just about every day but rarely pause to think about how very useful they are or how marvelous it is that we have them at all. Agricultural planning, religious and cultural ceremonies, navigation and timekeeping, economic and administrative coordination, political stability, and the keeping of historical records would be impossible in the absence of an accurate shared calendar.

A 2007 Wall Calendar by Claudio Elias

The Julian Calendar was a big improvement over its predecessor, the Roman Calendar, which was based on a lunar year. It’s easy to see the trouble with a purely lunar calendar. A period of twelve lunar months is roughly 354 days, 11-12 days shorter than a solar year, which meant that the Romans had to keep fiddling with theirs to correct the inevitable drift with respect to astronomical events like vernal equinox and winter solstice. The adding and removing of days was managed by a committee within the College of Pontiffs, a priestly group that had a lot of other duties to attend to.

Julius Caesar decided that Rome could do better. Acting with characteristic pragmatism and dispatch, he consulted an Alexandrian astronomer called Sosigenes and developed a solar calendar with a common year of 365 days. In reality, it takes approximately 365 days, 5 hours, 48 minutes, and 45 seconds for the earth to complete a full orbit around the sun. To make up the difference, the Julian calendar added an extra day every four years.

The Julian calendar was soon adopted throughout the Roman Empire and by various Christian churches. It is still used by the Berber people of North Africa and by some Orthodox churches, which employ it to calculate the dates of movable feasts, but in most of the world it was eventually replaced by the even more accurate Gregorian Calendar, the calendar with which most of us are familiar today.

The monastic community at Mt. Athos still uses the Julian Calendar.
Photo of Agiou Pavlou Monastery by Explorer1940.

At this point, you might be thinking, “Hold on. A calendar with three 365-day common years, followed by one leap year of 366 days—isn’t that what we use now?” Well, almost. The Gregorian Calendar is very similar to the Julian Calendar, with one small but important difference. Getting it adopted as the international standard was a wild ride that took 345 years…and, Lord willing, that’ll be the subject of my December post.

Kit Hawthorne makes her home in south central Texas on her husband’s ancestral farm, which has been in the family for seven generations. When not writing, she can be found reading, drawing, sewing, quilting, reupholstering furniture, playing Irish pennywhistle, refinishing old wood, cooking huge amounts of food for the pressure canner, or wrangling various dogs, cats, horses, and people. Visit her at https://kithawthorne.com/.