How ancient Egypt fixed the solar year at 365 days

The date printed at the top of the newspaper you picked up this morning comes from a very old idea. A year of 365 days, twelve months, and an extra day every four years. Its roots go back about 5,000 years to the banks of the Nile, where the ancient Egyptians first bound the year into a fixed count.

The Nile, the seasons and the count of the year

Life in ancient Egypt followed the flooding of the Nile. Each year the river rose, spread fertile silt over the fields and then receded. From this cycle the Egyptians made three seasons of the year: Akhet (flood), Peret (growing season) and Shemu (harvest and heat).

According to research by the Spanish astronomer Juan Antonio Belmonte, Egypt’s official or “civil” calendar had twelve months, each of exactly 30 days. Each month was divided into three parts of ten days. That made 360 days. Five extra days were added at the end of the year. The Egyptians called them the “five days upon the year”. In all, there were 365 days, a simple and dependable system.

The ancient Greek historian Herodotus travelled to Egypt. He wrote that, according to the Egyptian priests, they were the first people to divide the year into twelve parts. He said they added five days after twelve months of thirty days each to bring the count in line with the seasons. In his view, this was better than the Greek method.

When was this calendar created?

There is no single answer to this question. At one time the German historian Eduard Meyer calculated that 4241 BC was the “first certain date” in history, but later research rejected the claim. Richard A. Parker, an Egyptologist at the University of Chicago, argued in his well-known 1950 book that the civil calendar probably began sometime between 2937 and 2821 BC. Belmonte places it in the first half of the third millennium BC, when Egypt had come under one government and needed a common calendar for official work.

Parker also showed that Egypt did not have only one calendar. Lunar calendars continued to be used for religious festivals, while official business was conducted on the 365-day civil year.

Sirius and the wandering year

The Egyptian year began on the first day of the flood season, which they called the “opening of the year”. Many ancient writers linked this start to Sirius, the brightest star in the sky. After being absent for some weeks, it reappeared on the eastern horizon in the early morning in summer, at about the time the Nile began to rise. Experts disagree on whether the 365-day count originally came from observing Sirius, from observing the sun, from the moon, or from the average interval between Nile floods. Belmonte lists all four theories.

The problem was that the true solar year is about a quarter of a day longer than 365 days. The Egyptian calendar had no leap year, so every four years it fell one day behind the natural seasons. Over centuries, the “flood season” written on paper drifted away from the real seasons. According to Belmonte, it took about fifteen centuries for New Year’s Day to pass through all the seasons and return to its place.

Attempts at reform: from Canopus to Rome

In 238 BC, under Ptolemy III, a large council of Egyptian priests proposed adding one day every four years. Their decision, known as the “Decree of Canopus”, has been found carved in stone in three scripts. But the reform could not take hold at the time, and the old 365-day year continued.

Then came Rome’s turn. The Roman historian Suetonius writes that Julius Caesar corrected the disordered Roman calendar, made the year 365 days long and set the rule of adding one day every fourth year. To bring the seasons back to their proper places, the year of reform had to be made fifteen months long. Caesar had stayed in Egypt and knew its calendar. The new “Julian calendar” came into force on 1 January 45 BC. Some time later, under Emperor Augustus, Egypt’s own calendar also added a sixth extra day every four years.

The Julian year was 365.25 days, a few minutes longer than the true year. The difference, which built up over the centuries, was corrected in 1582 by the reform of Pope Gregory XIII. This “Gregorian” calendar is used across the world today.

Today’s calendar and the legacy of the Nile

Our Gregorian calendar did not come directly from Egypt, but its basic idea began there: keep the year equal to the sun’s cycle and follow the same rule every year. The direct heir of the ancient Egyptian calendar, Egypt’s Coptic calendar, is still alive. Coptic churches there use it, and many village farmers, Muslim and Christian alike, keep their farming calendar by it.

In Pakistan, the dates of offices, schools, banks and newspapers all run on this solar reckoning. When a farmer fixes the sowing date by watching the weather, or a student counts the days to an examination, they rely on a system whose first brick was laid on the banks of the Nile by people who kept track of the river’s rise and the return of the stars.