Priests and Popes and Caesar, Oh My: Evolution of the Modern Calendar
Marking the passage of time preoccupied our ancestors from the moment they looked to the heavens and wondered WTF. The never-ending journey of the sun, moon, and stars across the great expanse of sky reveals numerous methods of marking time, the most obvious to primitive humans being the passage of a day, and of a month.
Since a day is the time elapsed between two nights, and a month is the time elapsed between two new moons, both were fairly easy markers for early humans to figure out. A month was an especially convenient way to describe more recent happenings, and it also had an association with magic due to its lunar nature and influence on female fertility.
Human survival depended on the earth’s annual trip around the sun and the turning of the seasons. Measuring the exact length of a year is difficult, but for our ancient ancestors, less stringent parameters, such as when a certain tree would bloom, was enough to denote the beginning of a new year.
The ancient Egyptians understood that to calculate the measurement of a year it was necessary to know where the stars are in the sky at any given time. If a certain star is in a specific spot, it will be in that same location exactly one year later. The priests of Egypt used Sirius, the Dog Star, to predict the flooding of the Nile annually, which convinced worshippers of their priestly prescience.
And thanks to studying Sirius, the Egyptians became the first civilization to switch from a lunar to a solar calendar.
The ancient Babylonians also used a lunar calendar. Even today, the Muslim and Jewish calendars remain lunar-based. Nice if you like tradition, but using a lunar calendar poses a major problem as well.
A lunar month is 29.5 days, meaning 12 lunar months add up to 354 lunar days, which is about 11 days short of a solar year. To solve this problem, some lunar calendars add an extra month every now and then to make up for lost time, which is how it’s handled with the Jewish calendar.
The Egyptian priests’ study of Sirius allowed them to count the exact number of days in a solar year. They then sensibly arranged the lunar months into 12-month intervals, making each of them 30 days in length with five added days at the end of the year.
Sounds like a plan, but there’s a pesky little problem. Every four years Sirius shows up a day late. Why? The solar year is really closer to 365 days and six hours, which the Egyptians never took into account. This resulted in the calendar taking a backward slide as a lunar one would do, only at a much slower pace.
By the time of the Roman Empire under Julius Caesar, the calendar, which was out of sync by about three months, was in desperate need of tweaking. With the help of Sosigenes, a renowned astronomer from Alexandria, a new calendar was launched on January 1, 45 B.C., that came closer to the solar year than any of its predecessors. It became known as the Julian calendar. So, Sosigenes does the work and Caesar takes a bow. Isn’t that always the way?
Sosigenes informed Caesar that the actual length of the solar year is 365 days and six hours, as the Egyptian priests had known. Sosigenes felt the logical solution was to add a day to February, the shortest of the Roman months, every fourth year. This made up the difference, and with this clever idea, the leap year was born.
This calendar quickly spread across the entire Roman Empire and was used throughout Christendom for centuries. That is, until it turned out the solar year isn’t 365 days and six hours after all. It’s actually 365 days, 5 hours, 48 minutes, and 46 seconds. Obviously, this is one situation where it’s a plus to be anal. This only amounts to a discrepancy of a single day over 130 years, but when you’re talking long periods of time you have no choice but to nitpick. Somewhere down the road, another retweaking would be needed. But hey, that’s Future Human’s problem.
Meanwhile, the Olmecs in Central America devised a calendar quite like the one the Romans had whipped up. The Mayans fined-tuned it around the first century A.D. The Maya, having concluded that there were 365 days in a year, fashioned a calendar consisting of 18 months of 20 days each. They rounded out the year by adding five days at the end which are considered to be very unlucky under any circumstances. Another aspect unique to the Mayan calendar is what is called the Calendar Round, which is a cycle lasting 52 years in which every day has its own individual name — none are repeated. Must have been a bitch to keep up with holidays and birthdays.
The week is an entirely man-made unit of time, unlike the day, month, and year which rely on naturally occurring cyclical events. It is believed that the need for weekdays arose with the emergence of commerce, as ancient agricultural societies would have little need for such regimentation. (So yeah, the workweek is brought to you by — you guessed it — capitalism.)
There are two possible origins of the current seven-day week. The first is the Bible’s familiar story of creation when the seventh day is reserved for rest and worship. However, already existing Roman practices are the more likely source. What we would recognize as the modern week was in place by the first century A.D. in Rome. Mad heads already TFIG-ing in togas.
By the 1500s, the seemingly minor glitch of shorting the solar year by eleven minutes and fourteen seconds led to a ten-day gap between the calendar and real-time. This was particularly cluster-fuckish around the equinoxes, which were occurring ten days earlier than the dates on the calendar denoted.
Clearly something needed to be done, so Pope Gregory XIII took matters in his own hands by asking someone else, Christopher Clavius, a Jesuit astronomer, to solve the problem. Discovering that the error in question amounts to three days over a span of 400 years, he quickly devised a brilliant solution to the predicament.
Clavius calculated that years ending in ’00, or century years, only be leap years if they could be divided by 400. By doing so, three leap years are eradicated every three centuries, providing a tidy solution to a problem that had been plaguing humankind for eons.
The proposal, named after the Pope responsible for hiring its mastermind(ppppppffft), was introduced to the Papal States in 1582. The Gregorian calendar was quickly adopted by Spain, Portugal, France, and the Italian states the following year.
This was a time of great religious upheaval in Europe, and many of the Protestant states were in no rush to concede that the Bishop of Rome was right about anything. The Lutheran states of Germany finally got around to making the change in 1700, while Great Britain put it off until 1752.
Even though Britain had accrued a sizable gap of eleven days by that point, many people protested violently when the change was made, believing that eleven days were literally being stolen from their lives. (Their descendants would become flat earthers.)
Technological advances in the 20th century made it possible to further hone the accuracy of the Gregorian calendar, though the changes made won’t need to be implemented for many years to come. With the system we have in place now, one day will be added every 3,323 years, and years divisible by the number 4000 won’t be leap years.
And the beat goes on.
So, the next time you’re scribbling down your next dental appointment on your handy-handy calendar, take a moment to pause and appreciate its long and noble evolution. The calendar mailed to you during the Holidays by your insurance company sits on your desk thanks to Egyptian priests, Julius Caesar, and a Pope.
Not too shabby for something that’s usually tossed in the bin or used as a coaster.