Essential Facts About Who Discovered the Calendar

While looking at the 2017 calendar before the official toss, I realized I couldn’t remember how our calendar was created. I knew we used the Gregorian calendar and that it was based on the time it took for the earth to revolve around the sun. But that’s all I knew. So, I did a little research and am happy to share this information with you so that you’ll be smarter today than you were yesterday.

Early calendars were based on the cycle of the moon. A synodic month was the complete cycle of the moon phase. A solar year would be 12.37 synodic months. Days or months would have to be added in order to keep in line with the seasons.

A lunar calendar was of little help to hunters and farmers who needed to know rainy seasons, first frost and when to plant.

The Gregorian calendar is also known as the New Style calendar. In 1582, Pope Gregory the XIII introduced his new calendar because Easter was drifting further away from March 21st.

At the time, Europeans were using the Julian calendar which started in 45 B.C. With the help of his astronomer Sosigenes, Julius Caesar instituted a calendar based on the sun and not the moon. They figured a year to be 365 days and eventually realized that they needed to add that extra day to keep some consistency. What they didn’t realize was that a year is 365 days, 5 hours, 48 minutes and 46 seconds. The Julian calendar was a day off every 130 years.

By the time 1582, the seasons were off and Pope Gregory decreed a correction. Oct. 4 was to be followed by Oct. 15. This would put the vernal equinox the following year on March 21st. Leap years also needed adjusting so they decided that leap years would be omitted from years ending in hundreds unless the year was divisible by four.

The rest of the world was slow to accept the decree because it came from Catholic Rome. It took over 150 years for Britain and the colonies to adopt the same calendar. In 1752, Britain declared they would make the switch. September 2nd was to be followed by September 14th. When the days were added, Washington’s birthday moved from Feb. 11, 1731 to February 22, 1732.

The Julian calendar was based on a calendar the Egyptians established for the Nile Valley around 3200 B.C. As far as we know, they were the first to figure out the length of the year. They used the annual rising of the water, flooding that took place from June to October, growing from October to February and harvest from February to June.

The Egyptians eventually found a sign to mark the beginning of their year. The brightest star, Sirius the Dog Star rose in the morning in direct line with the rising sun. This became the beginning of the new year. They continued with the 365 day year not accounting for the extra 1/4 day. Over the centuries each named month gradually occurred in a different season.

Although most of the world runs on the Gregorian calendar. There are some people who still use a lunar calendar.

The Jewish calendar begins in autumn with the appearance of the new moon. Their year contains 29 or 30 day months and a leap year with an intercalary month.

The Christians base Easter on the first Sunday after the full moon which happens upon or next after March 21st.

Muslims also follow a lunar calendar but do not make adjustments to keep the calendar in line with the seasons. They follow a twelve lunar cycle calendar alternating between 29 and 30 days. Ramadan is the ninth month and each year it’s nine to ten days earlier.

As long as man’s life was marked by nature, he remained its prisoner.

Creating the week was a step toward controlling time. The early Romans lived by an eight-day week. Farmers worked for seven days and came to town on the eighth day. Somewhere along the time line the seven-day week was adopted. Why seven?

We can only speculate. Seven has always had some mystical essence. Seven wonders of the world, Japan’s seven gods of happiness, seven deadly sins, and most prominent, God created the heavens and the earth in six days and rested on the seventh day.

By the third century A.D., the Romans lived the seven-day week with each day being named after the current day planets: sun, moon, Mars, Mercury, Jupiter, Venus, Saturn. The days of the week in European languages still use the planets. For example, in Spanish, martes is Mars, miercoles is Mercury, jueves is Jupiter, viernes is Friday.

It’s amazing  that the calendar we follow today dates back to 1582. Pope Gregory and his astronomers had no computer models to look at or apps to do their math. They observed and calculated in an effort to move mankind one step closer to controlling its surroundings.



Boorstin, Daniel. J. The Discoverers.

Cohen, Jennie. 6 Things You May Not Know About the Gregorian Calendar. History Channel website.


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