For: days of the week

A week (also called sennight or sevennight) is a unit of time longer than a day and shorter than a month. In most modern societies the week is a period of seven days. The weekly cycle of seven days runs independently of the cycle of a calendar. The common denominator in both cases is the day.

Europe and Near East

The origin of the concept of the week may be attributed to Genesis 1 and 2 in the Bible, which contains the creation account of the earth, animals, and man in six days, with the sabbath of rest on the seventh day (Genesis 2:2-4). Its existence in ancient cultures may be traced to a divine or spiritual origin for this institution, since there is no celestial explanation to account for it, such as exists with the day, the month, and the year.

Various sources point to the seven day week as having originated in ancient Babylonia or Sumer. It has been suggested that a seven day week might be much older. The seven day planetary week originated in Hellenistic Egypt.

The 1943 Universal Jewish Encyclopedia volume 10 page 482, edited by Isaac Landman under the article “Week”, written by Simon Cohen, Director of Research, summarizes:

Meanwhile, the Roman Republic and then Empire, like the Etruscans, used a "market week" of eight days (known as the nundinal cycle). From around the 1^st century CE, with the spread of Christianity, the Roman eight day week was replaced gradually by the seven day week.

The seven day weekly cycle is known to have remained unbroken in Europe for almost two millennia despite changes to the Alexandrian, Julian, and Gregorian calendars. The date of Easter Sunday can be traced back through numerous computistic tables to an Ethiopic copy of an early Alexandrian table beginning with the Easter of 311 CE as described by Otto Neugebauer in Ethiopic astronomy and computus. Only one Roman date with an associated day of the week exists from the first century and it agrees with the modern sequence, if properly interpreted. Jewish dates with a day of the week do not survive from this early period. In the case of the Jewish week, it had been in use for at least 1,000 years before its adoption by the Roman Empire.

The Jewish and Christian seven-day week is modeled on the biblical creation story, in which God created the universe in six days, then rested on the seventh.

Other theories speculate that the fixed seven-day period appeared due to evenly dividing a lunar month into quarters.

The seven-day week became established in both the West and East according to different paths:

Hindu seven-day week

Hindu civilization used a seven-day week. It is mentioned in the RamayanaFact: date=September 2008, a sacred epic written in Sanskrit about 500 BCE, and translated as follows:

The meaning of the name of the days of the week in Sanskrit, above, is equivalent to English names: e.g., "Shani-Vaar," where Shani = Saturn and Vaar = Day.Fact: date=April 2008