How Was The Calendar Invented?

People often take time for granted. They usually aren’t curious why or how it exists; they only accept that it does. Your birthday could fall during the winter, the week always begins on Sunday, and February is unusually short and has an additional one day every four years. It is simply the way things work.

This, however, was not always the case. Ancient societies, including the Egyptians, Babylonians, and Romans, significantly impacted how we tell time and dates and the current calendar we use today! The story behind the invention of the Gregorian calendar as the international standard of time worldwide is extra complex than most people may think. 

However, prior to the Gregorian calendar, the Sumerians were among the first to employ calendars in Mesopotamia during 3100 BCE. Based on whether or not the first day of the month was a full moon, each month on this calendar consists of only 29 or 30 days. Whatever the case, there have always been 12 months each year. 

date change from Julian Calendar to Gregorian Calendar

Then in 2510 BC, the Egyptians constructed their first calendar, which made use of the cycle of the moon and Sirius, a star, to tell time. The Egyptian calendar comprises 12 months, the same as the Mesopotamian calendar, but it had an additional five days in the year.

King Romulus instituted the first Roman calendar in 738 BC. This calendar only included ten months, beginning in March and finishing in December. There were 354 days in one Lunar year, but because the Romans felt that even numbers are lucky numbers, they rearranged the calendar to have an even number of days every month. As a result, the seasons were out of synchronization the following years.

Most people consider zodiac signs to reveal your personal traits and values. Some say it can even foresee your future. The Chinese lunar calendar, based on zodiac and astronomy, initially developed in China around the fifth century B.C. 

Another calendar invention during 500 BC was the Mayan calendar. Most people associate “Doom’s Day” with the Mayan calendar. The BBC News said this was “a major deal,” as the calendar concluded in 2012 merely because it marked the conclusion of one cycle and the start of the other.

Mesopotamia, Rome, and Egypt all had calendars, so around 499 BC, the Babylonians decided to come up with their own. Their lunar calendar, which included the 13th month every two or three years, influenced the Jewish calendar, which is still in use presently. 

Also, in 400 BC, the Greeks had had inventions of various lunisolar calendars that they used to tell time. The Athenian calendar, also referred to as the attic or civic calendar, was the most widely used. Still, the Greeks also developed the Conciliar, Metonic, Olympiad, and Seasonal calendars. They based each calendar on the moon and star cycles, along with solar equinoxes.

The ancient civilization used the earlier Julian Calendar prior to adopting today’s modern Gregorian calendar. The majority of the Western world has used the Julian calendar. It was named after Julius Caesar and developed around 45 BCE, which would have been the year 709 for them because their calendar began on the year Rome was established. 

The Julian calendar consists of 365 days per year, including one additional day every four years. It was remarkably similar to the actual duration of the year, but the Julian calendar wasn’t the greatest —  it gradually drifted off course over the following centuries. The calendar was reasonably accurate, but it made the year 11 minutes and 14 seconds longer on average. The ancient civilization didn’t address this minor issue until 1582.


Hundreds of years after, the Gregorian calendar, also referred to as the Western or Christian calendar, was eventually adopted in 1582 by most countries in the world. The Julian calendar had strayed by a whole ten days – this 11-minute anomaly in the Julian calendar caused a conflict on dates, especially with the Easter season. 

They expected to observe Easter on the Sunday following the first full moon after the spring equinox, or March 21st. However, as the date drifted farther and farther each year, Pope Gregory became alarmed, and he appointed Italian scientist Aloysius Lilius to correct it.  After analyzing the calculations, he concluded that the Catholic world would have to go back ten days to stay up to date.

The Gregorian calendar is more credible in telling time than the Julian calendar. It still has a leap year every four years, except years divisible by 100, unless that year can be divided by 400. However, everything has its flaws, and it’s no exception with the Gregorian calendar. Scientists say that 4909 is going to be a full day.

Many people are wondering where the months of the year got their names. The names of the months based on Latin are used in many different languages, including English. Meanwhile, certain languages, such as Czech and Polish, have very distinct names for the months. Nevertheless, here is the list of the origins of the names of the months. 

January- The inspiration for this name was the Roman god Janus, the guardian of gates and doors. Janus has two faces, one staring into the past and one for the future. In ancient Rome, the doors of the Janus Temple were open during periods of war conflict and were shut during peaceful times.

the Roman god Janus

February- Originated from the word “Februa,” which means “to cleanse.” The Roman calendar month, Februarius, was named after Februalia, a festival of cleansing and repentance that occurred during ancient Roman times.

March- It is named after Mars, the god of war. 

April- The month got its title after Aphrodite, the goddess of love, or after the Latin word “aperire,” which means “to open.”

May- May was most likely named after the goddess Maia, who controlled plant growth and development in ancient Roman myth. The name may also come from the Latin term “maiores,” which means “elders,” honored throughout this month. Maia is a nurturer and an Oscan earth goddess, which could explain the association with this springtime season during this month.

June- It most likely takes after Juno, goddess of marriage and women’s well-being. It is also possibly derived from the Latin term “juvenis,” which means “young people.”

July- It was named honoring Julius Caesar following his death in 44 B.C.E. Julius Caesar created one of the most significant accomplishments of humankind in 46 B.C. when he created the Julian calendar also with the assistance of Sosigenes. The calendar he made was the forerunner of the Gregorian calendar, which we currently use.  But before that name, it was known as Quintilis, from the Latin word Quintus, which means “fifth,” since it was the fifth month in the ancient Roman calendar.

statue of the head of Julius Caesar

October- In the old Roman calendar, October was the eight-month, hence, the name. It originated from the Latin word “octo,” which means “eight.”  When the Romans made the year into twelve months, they tried to change the name of this month into numerous Roman emperors, but October persisted.

November– Named after the Latin word “novem,” which means “nine,” as it was the ninth month in ancient Roman times.

December- The name was derived from the Latin word “decem,” which means “ten,” because December was the tenth month during the ancient Roman period.