Calendar in ancient culture

Calendars are manmade tools used to track time. They have become almost indispensible tools of human civilization.

Ancient cultures develop calendars to keep track of longer stretches of time that coincide with the four seasons.

Calendars are based upon astronomical observations, marking the passage of time using the phases of the moon and movement of the Sun. Civilizations from Asia to the Americas develop calendars based upon the phases of the moon.

Early calendars were usually for agriculture, financial, religious and political uses and often did not include a year count. The first historians to use calendar date systems for relating events were the Greek historians.

Ancient Greek calendars go back to early Antiquity but evidence of how they were structures and reckoned begins only in the sixth century BC. In general the calendars of Greece were lunar, but their lunar character could be disrupt by deliberate interference or tempering.

The main Athenian calendar is often called ‘archontic’ or ‘festival calendar’ - although its use went far beyond the determination of festival dates – to distinguish it from the so-called ‘prytanic calendar’, peculiar to Athens, that was used at Athens alongside it.

It wasn’t until Rome was fully under the rule of Augustus Caesar that calendars were used to refer to particular year names or numbers and month and day dates.
Calendar in ancient culture

Cleostratus of Tenedos astronomical calendar

Greek astronomer, Cleostratus of Tenedos (520-432 BC) who lived rather outside the Ionian zone, made two important contributions to astronomy.

One was an improvement in the calendar, involving a better measure of the solar year. Together with Eudoxus, Cleostratus is credited with trying an 8-year cycle to commensurate the lunar and solar calendars.

Cleostratus proposed in the course of the eight years, to insert three intercalary months, of 30 days each, at the end of the third, fifth and eighth years respectively. He thus got a period of 2922 days, comprising 99 lunar revolutions.

The other was the knowledge of the signs of the zodiac and constellations in it which he introduced from Mesopotamia.

Zodiacal signs are frequently encountered upon Mesopotamia boundary stones and indicate the time of year at which the stones were erected.
Cleostratus of Tenedos astronomical calendar

Ancient Chronology; Calendars and Measurement of time

Ancient Chronology; Calendars and Measurement of time
The frequent and obvious cycles of the moon furnished the earliest measure of time, each cycle being a lunar month.

In Sumer each month began with the new moon, which was carefully observed by the priests.

There were twelve months in the year and when the accumulated shortage (about 11 days each year) became too great and extra month was intercalated, a practice that continued until the reign of Darius (521-485 B.C).

At the summer solstice the rising sun shining straight down the main street of Babylon, furnished a gauge for adjustment of the calendar to the solar year.

In the Lower Egypt the year commenced with the annual rise of the Nile, which begins rather suddenly about the middle of July, a date marked astronomically by the rising at sunrise of the Dog Star, Sirius, the brightest of the fixed stars.

This is a striking event, nowhere more brilliant than in the vicinity of Cairo. In course of time it became evident that the return of Sirius was five days later than the completion of the year of twelve 30 day months, and the year was accordingly lengthened by the addition of five holidays.

The residual shortage of about 6 hours resulted in a slow periodic change of the beginning of the year which would return to its original position in about 1,458 years.

By means this “Sothic cycle,” that the civil calendar of Egypt was introduced in 4236 B.C. not only the earliest fixed date in history, but also the earliest date in the intellectual history of mankind.

The year was divided into three seasons – the inundation, the season of cultivation, and the harvest season.

The months, probably lunar at first, became 30 days, and this continued into historic time.

An edict of 238 B.C. introduced the leap year but the innovation was afterwards forgotten.

The artificial subdivision of the day and night into hours was achieved in Egypt by means of some form of the sun-dial for the day and of the water clock, or clepsydra, for - day and night having each twelve hours of varying lengths.

The earliest time piece known is an elaborate water-clock described by its maker Amenemhet on the wall of his tomb-chapel in the cemetery of Egyptian Thebes about 1550 B.C.

The Babylonians on the other hand by measuring the amount of water escaping slowly from a vessel full ascertained that the tome from the first appearance of the upper edge of the Sun to the moment the whole disk was visible was 1/720 of the entire tome from one sunrise to the next.

This period of day and night was then divided into 12 equal parts, one of which would thus equal twice the modern hours, and is the time required for the sun to travel 60 times its own diameter.
Ancient Chronology; Calendars and Measurement of time