THE ANCIENT ORIGINS OF OUR MODERN CALENDAR

TIMELINE OUTLINING THE HISTORY OF THE CALENDAR; GRAPHIC BY JULIETA ORTIZ

The calendar that we use today was a revised version of a reform of a calendar made over 2,700 years ago and has undergone many changes and adjustments. In the same way people have evolved and improved over time, so has the calendar. 

The Gregorian calendar is what we use today in the U.S. and is also used by the majority of other countries. The Gregorian calendar was a reform of the Julian calendar that Pope Gregory XIII made to fix an error that was made during the formation of the Julian calendar about leap years. The miscalculation concerning leap years caused many events to take place in the wrong season and led to issues in determining when Easter was. To understand the Gregorian calendar and the changes he made more completely, we first must look at the calendars that preceded it. 

According to legend, it was the founder of Rome, Romulus, who created the Roman calendar around 738 BC. It was 10 months long and consisted of 304 days while the remaining days were during the winter and were left as a nameless gap. The early Roman calendar had March as the first month of the year, which was named after the god Mars, the Roman god of war. The calendar was based on lunar cycles and agriculture. In 713 BC, Numa Pompilius added January and February to the Roman calendar. He replaced March as the first month with January and then placed February at the end. It made more sense for January to be at the beginning as it was named after Janus, the Roman god of beginnings, doors, and gates. Eventually, in 452 BC, February would be moved to be the second month between January and March. 

During the first century BC, lots of confusion came about the calendar. The calendar was based on moon cycles and the year consisted of 355 days, roughly 10 days shorter than the solar year. Every couple of years, an extra month called Mercedonius, of 27 to 28 days was added to the calendar to keep it in line with the seasons. The confusion began with the College of Pontiffs and the Pontifex Maximus who had authority over the calendar and would use their power to shorten or lengthen the terms of politicians. Julius Caesar made a reform in 46 BC and created the Julian calendar.  

The Julian calendar had 365.25 days, which is just slightly off. According to NASA, “The true length of a year on Earth is 365.2422 days”. Within the year there were 12 months which all had 30 or 31 days, except for February. The Julian calendar introduced leap years, every 4 years there would be a year with an extra day. That left February with 28 days in common years and 29 days in leap years. However, instead of February 29th, they would repeat February 23rd during leap years. In 46 BC, Caesar wanted to align the civic and solar calendars so he added days to that year of 46 BC which ended up with 445 days. Due to all the confusion and complications, the calendar was not operating smoothly until 8 AD. The Julian calendar was used until 1582 AD when the Gregorian calendar was created. 

The small error that was made during the creation of the Julian calendar caused the days to regress about one day per century which would have been around 14 days by Pope Gregory’s time but he based his restoration on the vernal equinox. So to make up for this, the calendar went from October 4th to October 15th. In the Gregorian calendar, the system of leap years continues but there is a slight difference. Every 4 years is a leap year unless it is a century year that is not evenly divisible by 400. For example, the year 2100 would not be a leap year because it is not evenly divisible by 400. Compared to the Julian calendar which has a leap year every 4 years regardless. Another difference is that the Julian calendar repeated February 23rd as a leap day while the Gregorian calendar has February 29th as a leap day. 

Some places adopted the Gregorian calendar very quickly, for example, Spain, Portugal, the Roman Catholic German states, and the Italian states. While some places took a while, for example, Great Britain and its colonies in 1752, Japan in 1873, and Greece in 1923. Some countries use the Gregorian calendar along with religious calendars but others don’t use the Gregorian calendar at all. 

From the Roman calendar to the Julian calendar and to the Gregorian calendar, there have been many changes and adjustments to improve the accuracy. It took some time, but it’s important to recognize that each small revision was essential and led us to the accuracy we have today. Looking back at all of this connects us with the past of humanity and can be encouraging that each small improvement will add up to be something extraordinary. The information in this article was all sourced from Britannica unless cited differently.