More From My Study Of Time: Creating A Calendar

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by Mary Jo Shannon

Calendars are essential for organizing our lives. We usually have several – one in the kitchen to keep track of everyone, one to carry with us, and another on the computer. We give little thought to how our calendar came to be. I found the story of its evolution fascinating

Observation of changes in the moon and correlating changes in the seasons, led early men to believe the moon controlled the seasons. They developed a lunar calendar, based on the moon’s cycles – three new moons of spring (months; each moon from new moon to new moon was 29 ½ days), three new moons of summer, three new moons of autumn, and three new moons of winter. The lunar calendar was inaccurate, because of the mistaken assumption that the moon controls the seasons.

About 6,000 years ago, the Egyptians celebrated the beginning of their year (near the end of what we know today as the month of June) when, after a long absence, Sirius, the Dog Star appeared once again in the eastern sky. For five days they celebrated with feasts and dancing in honor of their god, Osiris.

When Sirius appeared, the mighty Nile flooded, spreading rich black soil over the flat fields for about three months. Then the waters receded and they could plant crops to grow and ripen in the hot desert sun. When the harvest ended, the cycle would begin again.

The Egyptians were the first people to invent a solar calendar, based on the apparent movement of the sun. Their year consisted of twelve months of 30 days each. Five extra days of feasting added after the twelve months made a year of 365 days, almost accurate. (Today, thanks to precise scientific instruments, we know that the year, measured by the time it takes the earth to orbit the sun, is actually 365 days, 5 hours, 48 minutes and 46 seconds long.)

As they carefully recorded the time when Sirius appeared each year, Egyptian astronomers discovered the year is actually 365¼ days long (only 11 minutes and 24 seconds off modern calculations!).

They wanted to add another day every four years to make up the lost time, but their priests who controlled the calendar considered the calendar sacred and refused to alter it. So eventually, this solar calendar was also out of synch with the seasons, although not as much as lunar calendars were.

The lunar calendar caused problems because the moon’s cycle of about 29 days only seemed to coincide with the seasons. Changes in the seasons are actually caused by the earth’s movement in its orbit around the sun, and not by the phases of the moon.

An improved solar calendar invented by the Egyptians around 4236 B.C. was on the right track, but it was six hours off.  Six hours spread over a whole year were not noticed immediately.  But after about 1460 years the months were no longer in the right seasons.

In 48 B.C., when Caesar conquered Egypt, the Egyptian solar calendar fascinated him (almost as much as the beautiful Cleopatra!).  He brought an Egyptian astronomer named Sosogenis to Rome to reform Rome’s calendar.

Sosogenis developed a calendar for the Romans with 365¼ days. He calculated that in four years, that fraction would equal an extra day. So on the fourth year, he added a day, giving the year 366 days. That fourth year was called Leap Year.

The names of the twelve months in the lunar calendar remained the same, with one exception. To honor himself, Julius Caesar changed the fifth month, Quintilis, to “Julius.”

How should the days be divided between twelve months? Caesar decided to alternate months of 30 days and 31 days, except for February, which would have 29 days ordinarily and 30 days on Leap Year.

This logical arrangement was upset later by the vanity of Augustus Caesar, who was the next ruler of Rome.  Augustus renamed Sextilis “Augustus” for himself.  Then, realizing that “Julius” had 31 days and “Augustus” only 30 days, he took a day from Februarius to add to “Augustus.” Now February had 28 days, with 29 on Leap Year, and there was no logical system!

Although the new Roman calendar worked better than the old one, it needed adjusting to make the spring equinox come at the right time in March.  By 46 BC, it was two months out of line. Julius Caesar added those two extra months to that year, between November and December.

The year 46 B.C. had 445 days! Caesar proudly announced that this would be “the last year of confusion.”  He referred to the confusion caused by the old calendar that announced spring in the middle of winter. But the added months caused so many problems throughout the Roman Empire that people called it simply “the Year of Confusion.”

Once the Year of Confusion passed, the Romans were glad to have a standard calendar that was not constantly shifting with the seasons and that gave them more control over their lives. Excavations of ancient Roman cities show that calendars were publicly displayed, carved in stone and painted on walls.

The Julian Calendar, as it was called, was used throughout the Roman Empire, all over Europe and Africa and was the official Calendar until 1582 A.D.( For 1628 years!)

Why did we stop using it?  That’s another story!