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God's Mysterious 7-Day Cycle
in plants, animals and MAN!
(Part 1)

Society's seven-day calendar week is the only major rhythm of human activity that is totally oblivious to external nature. This so-called "social week" rests on mathematical regularity alone. We may casually assume that our week is really a division of the moon cycle. If that is our assumption, we forget that the lunar cycle is not a twenty-eight-day cycle, but approximately twenty-nine days, twelve hours, forty-four minutes and three seconds -- or 29.5306 days between new moons. A precise quarter of the lunar cycle amounts to the uneven figure of 7.38625 days. So any week using that true length would begin at different times of the day every time the cycle started. There is just no way to neatly divide the lunar cycle into weekly blocks of complete days. (1)

Then what about the sun? Doesn't the cycle of seven relate to the center of our solar system? Again, no! The 7-day week is also independent from the annual solar cycle of 365 1/4 days. A "year" of 52 weeks would have just 364 whole days. Nor is the week in harmonic sympathy with the star year of 366 1/4 days. Star days or "sidereal days" are about four minutes shorter than solar days (an observer will see a particular star at the same position four minutes earlier on successive nights). In short, there are no known external rhythms in nature that could explain the near universal existence of the seven day social week.


Yet, the importance of the seven-day week -- or heptad, a series of seven -- is monumental. Eviatar Zerubavel, in his book The Seven Day Circle (The History and Meaning of the Week), notes that:

"a continuous week, for the establishment of settled life with a high level of social organization [is indispensable] . . . . Only by defining the week as a precise multiple of the day, rather than as a rough approximation of a fraction of the lunar month, could human beings permanently avoid the problem of having to handle loose remainders and, thus, introduce into their lives the sort of temporal regularity that they could never attain with the quasi week." (2)

Professor Zerubavel is saying that a regular, predictable week plays a major role in developing our civilization.


We take for granted the commonness of a world-wide seven-day week, but that hasn't always been the case. "Weeks" varying in length from three to nineteen days have existed in past cultures. In parts of Africa three, four (especially along the Congo river), five, six and eight day weeks are found, and always in association with market days. Along the Congo the word for week is the same as the word for market. In North America the Mayas of Yucatan -- skilled mathematicians and pyramid builders -- had clusters of five-day weeks. In South America the Muyscas had a three-day week, the Persians and Malaysians a five-day week. (3)

The ancient Etruscans, who inhabited the land the Italians do now, had an eight day market week which they passed on to the Romans no later than the sixth century B.C. As Rome expanded it encountered the seven-day week and for a time attempted to include both. But the coexistence of two weekly cycles was unworkable. The popularity of the seven-day rhythm won out and the eight-day week disappeared forever. (4) Emperor Constantine eventually established the seven-day week in the Roman calendar and in 321 A.D. set Sunday as the first day of the week.

Apart from the biblical record, historians have had difficulty placing the precise beginning of the seven-day week. It is simply acknowledged as an ancient practice of very early origin in the evolution of civilization. (5) The historical record becomes specific, however, with the appearance of Israelite religion and culture. In the millennium before Christ the distinctive of Israel's (and Judaism's) seven-day week became widely known. Its special seventh day devoted to worship and rest -- the Sabbath -- became an identity trademark that has endured to the present.

Jeremy Campbell, in his comprehensive inquiry into the human nature of time, jauntily titled Winston Churchill's Afternoon Nap, gives Israel full credit for introducing the seven-day week. "In all the ancient world, so far as is known, there was no seven-day calendar cycle except for the Jewish week, which existed at the very beginning of the monarchical period in Israel [approximately 1000 B.C.] and perhaps even earlier than that. A seven-day week was unknown among the ancient Greeks, whose holidays were held at very irregular intervals, since they fell on the days of religious feasts in different cities up and down the country.

Besides the Israelite heptad, or seven day period, another tradition contributed to the forming of our modern seven-day week. Long before the Greeks, Babylonian astronomers began to identify and name the seven heavenly bodies (sun and moon included as "planets") which they observed moving about the sky. Lacking our modern telescopes, they did not spot Uranus, Neptune or Pluto. Neither did they name weekdays after those seven "planets." Assigning planets to the days of the week is attributed to the Egyptians. But once a planet became attached to a day, the seven day "planetary week" came into existence.

". . . The planetary week, however, was a relative newcomer compared with the Jewish week. . . [and] may have evolved from [it], and was undoubtedly influenced by it. Presumably the seven-day structure of the Jewish week came first, and later people began to call the days of the week after the names of the planets. Our modern week is a blend of both traditions." (6)

Zerubavel concludes that "the astrological seven-day week, which evolved in Alexandria during the second century B.C., was introduced to the West through Rome sometime toward the end of the first century B.C. If it was Alexander the Great's conquest of Greece, Babylonia, and Egypt that, in bringing those three civilizations together, was indirectly responsible for the evolution of the astrological week in the first place, it was Julius Caesar's conquest of Egypt that, in making Rome heir to the glorious Hellenistic heritage, was responsible for importing that oriental cycle to the Occident." (7)

He also concludes that while the Jewish and astrological weeks evolved independently, they were eventually joined together by another power. ". . . It was the Church that was responsible for integrating the Jewish and astrological weeks together and spreading the seven-day cycle throughout most of the world. (8) Yet Christianity was by no means the only carrier that helped spread the Jewish week around the globe. Starting from the seventh century, Islam was responsible for importing this seven-day cycle to the east coast of Africa, the Sudan, Central Asia, large parts of North and West Africa, and even as far as to the Malay peninsula and parts of Indonesia." (9)

Both Christianity and Islam inherited the seven-day week from the Jews. Both established worship days separate from the Jews: Sunday for the Christians, Friday for the Moslems -- both days touching the original Sabbath. These three religions with their three worship days clustering together have played key historical roles in bringing the beat of a seven-day week to all the world.


Because of the bond between religion (Christianity especially) and the week, there have been two major attempts in modern times to obliterate the seven-day week in favor of a different length week. The first attempt came in the late 1700s. The humanistic French Revolution promised the people a new Age of Reason to replace regressive religious superstitions. A new secular, "rational" week of ten days was devised and approved by the ruling Convention in October, 1793. (11) The ten-day "decade" was patterned after the decimal principle, having ten days divided into ten hours, of 100 minutes each with each minute divided into l00 decimal seconds. Every tenth day, the "decadi" was reserved for rest and celebration of various natural objects and abstract ideas. Notre Dame was renamed the Temple of Reason.

"The real target of the reform campaign," notes Zerubavel, "was the Christian [Church]. . . and from a symbolic standpoint, the abolition of the seven-day 'beat' expressed the wish to de-Christianize France far more than the attempt to make life there more 'rational.'" (12) During the Reign of Terror the ten-day "decade" was imposed by force. Churches were closed and allowed to open only on the tenth day. People were even forbidden to wear their good clothing on the traditional Sunday, with severe fines and even jail sentences given to violators. Religion, however, proved too resilient and the attempt to destroy the seven-day week (1793-1805) failed completely . . . as did the First Republic of France.

Not learning a thing from France's failure, the Communists ruling the Russian Revolution tried a second, even more radical experiment 140 years later. Their aim was the same: abolish religion by abolishing the seven-day week. The Soviet scene was a five-day continuous work week which called for 80 percent of workers to be on the job on any given day -- a plan which left 20 percent to share a day off. There was no longer a national day off. The advertised reason for the new rotating five-day week was to increase production.

After eleven years of disappointing production and epidemic irresponsibility in the work place (1929-1940) Stalin called it quits and gave the Soviet people back their seven-day week. Concludes Zerubavel, "In both France and the Soviet Union, some desperate attempts were made by two of the most ruthless totalitarian regimes in history to completely destroy the Judeo-Christian, seven-day week. In both societies, to this day, it still remains the dominant 'beat' of social life." (13)


In light of these massive failures, we must face the question "why seven?" Since the seven-day cycle is not a naturally occurring event in our external environment, can culture alone explain how a whole society six billion strong now beats to a seven-day rhythm?

Tracking the development of the seven-day week in human events, as we have briefly summarized above, has been a far easier task for historians than explaining how the cycle originated in the first place. Researchers really have only two choices: 1) say that the week is a cultural/religious invention of unknown date which gradually took root in the ancient world, evolving with time to the near universal acceptance we find today; or, 2) take the biblical record of the origin of the week (Genesis, chapters 1 & 2) at face value -- it was made by God at creation.

For convenience we may call option one -- a standard, textbook explanation -- "the cultural/religious outgrowth model;" option two naturally becomes "the biblical model." It comes as no surprise that most modern historians reject the second, or biblical model, and spend their ink documenting the first one, attempting to explain the strange phenomenon of a seven-day week.

However one rates those attempts, recent discoveries revealing innate body rhythms of about seven days now call that cultural outgrowth model into question.

The relatively new science of chronobiology has uncovered some totally unexpected facts about living things, as Susan Perry and Jim Dawson report in their book The Secrets Our Body Clock Reveal. "Weekly rhythms -- known in chronobiology as "circaseptan rhythms" -- are one of the most puzzling and fascinating findings of chronobiology. Circaseptan literally means "about seven;" see chart. Daily and seasonal cycles appear to be connected to the moon. But what is there in nature that would have caused weekly rhythms to evolve?

"At first glance, it might seem that weekly rhythms developed in response to the seven-day week imposed by human culture thousands of years ago. However, this theory doesn't hold once you realize that plants, insects, and animals other than humans also have weekly cycles. . . . Biology, therefore, not culture, is probably at the source of our seven-day week." (14)

Campbell summarizes the findings of the world's foremost authority on rhythms and the pioneer of the science of chronobiology: "Franz Halberg proposes that body rhythms of about seven days, far from being passively driven by the social cycle of the calendar week, are innate, autonomous, and perhaps the reason why the calendar week arose in the first place." (15)

What a bombshell!


Mankind has always been aware of rhythms -- they surround us. We live with daily rhythms of tides, light and darkness, monthly rhythms of the moon, seasonal rhythms of birth, growth, harvest, hot and cold, and annual cycles of the sun, migrations, floods and drought. We have also observed cycles in our bodies which interact with those around us such as our daily sleep rhythms, daily temperature and blood pressure fluctuations, and the menstrual cycle which follows the lunar cycle precisely averaging 29.5 days.

However, until recently science has been aware of only the more obvious rhythms. Now the new science of chronobiology has begun to roll back frontiers revealing a universe replete with rhythms.

Franz Halberg, the brilliant scientist and founder of modern chronobiology, first began his experiments in the 1940s and now heads the Chronobiology Laboratories at the University of Minnesota. He offers us this rather detailed description of his field:

"Chronobiology is the eminently interdisciplinary science of interactions in time among metabolic, hormonal, and neuronal networks. It involves anatomy, biochemistry, microbiology, physiology, and pharmacology, at the molecular, intracellular, intercellular, and still higher levels of organization. The compounds coordinating a time structure -- proteins, steroids, and amino-acid derivatives -- provide for the scheduling of interactions among membrane, cytoplasmic, and nuclear events in a network involving rhythmic enzyme reactions and other intracellular mechanisms. The integrated temporal features of the processes of induction, repression, transcription, and translation of gene expression remain to be mapped . . ." (16)

Simply put: Chronobiology is the study of how living things handle time.

Chronobiology is no longer a minor science. Perry and Dawson note that it ". . . is now being studied in major universities and medical centers around the world. There are chronobiologists working for the National Aeronautics and Space Administration (NASA), as well as for the National Institutes of Health and other government laboratories. Chronobiology is becoming part of the mainstream of science, and it is changing our way of looking at life and time." (17)

"Don't confuse the science of biological rhythms with the quackery of biorhythms," warn Perry and Dawson. "The two are as unlike each other as astronomy and astrology." (18)

There are five major rhythms that beat in our bodies to insure our health and happiness (see chart below). The daily or circadian rhythm (from the Latin for "around a day") is the easiest to detect and measure. We are born with our own set of circadian rhythms that in time become synchronized with our environment. Our rhythms vary slightly from individual to individual (23.6 hours, 24.3 hours, 25.4 hours, etc.) and they usually shorten as we age. For some unknown reason, women tend to have shorter circadian cycles than men.

Your Inner Rhythms

Type of Rhythm Length Examples
Ultradian Less than 24 hours Heartbeat. 90-min. fluctuations in energy levels & attention span. Brain waves.
Circadian About a day Temperature. Blood Pressure. Sleep/Wake Cycle. Cell Division.
Circaseptan About a week Reject of organ transplants. Immune response to infections. Blood & Urine chemicals. Blood Pressure. Heartbeat. Common Cold. Coping hormones.
Circatrigintan About a month Menstrual cycle
Circannual About a year Seasonal depression. Sexual drive. Susceptibility to some diseases.

If all our individual cycles vary from a precise 24 hour day or 168 hour seven-day week, wouldn't we in time get terribly out of sync?

"Fortunately," write Perry and Dawson, "our bodies are able to reset themselves each day to the twenty-four hour rhythm, thanks to many powerful time cues. Chronobiologists call these cues zeitgebers, German for 'time givers.' Some can be found outside our bodies, some are located within, and others are part of our daily lives . . . .

"As if we didn't have enough zeitgebers to keep our bodies in sync with the world, our internal rhythms also help synchronize each other, for none of the myriad rhythms within our bodies works in isolation. Some rhythms rise while others fall -- like a modern dance in which the dancers move seemingly independently of each other, but which actually has been carefully choreographed. The dance is so complex that chronobiologists are only beginning to understand the interrelationships of the rhythms." (19)


The most intriguing of all biological rhythms are those set to a clock of about seven days. In his chapter "The Importance of Time," Jeremy Campbell reports:

"These circaseptan, or about weekly, rhythms are one of the major surprises turned up by modern chronobiology. Fifteen years ago, few scientists would have expected that seven-day biological cycles would prove to be so widespread and so long established in the living world. They are of very ancient origin, appearing in primitive one-celled organisms, and are thought to be present even in bacteria, the simplest form of life now existing." (20)

One of Franz Halberg's amazing discoveries is that of an innate rhythm -- about seven days -- occurring in a giant alga some five million years old on the evolutionary time line. Because this microscopic cell resembles a graceful champagne glass, the alga (plant) is popularly known as mermaid's wineglass (Acetabularia  mediterranea). When this "primitive" alga is subjected to artificial schedules of alternating light and dark spans of varying length over many days, this single intact cell is somehow able to translate all that manipulation of light and darkness into the measurement of a seven-day week!

As Campbell says, this inherent rhythm has to do with the internal logic of the body, not with the external logic of the world. Many more examples could be given. Involved experimentation with rats, face flies, plants and other life have revealed circaseptan rhythms similar to that of the mermaid's wineglass. (21)

If the seven-day week is an invention of culture and religion, as most historians would have us believe, how do we explain innate circaseptan rhythms in "primitive" algae, rats, plants and face flies? These forms of life have no calendar, can't read the Torah and don't know Saturn from Santa Claus.


[1]. Eviatar Zerubavel, The Seven Day Circle (Chicago: Univ. of Chicago Press, 1985), p. 9.
Zerubavel, p. 10: emphasis added, words in brackets adapted from the author himself.
Article "Week," Encyclopedia Britannica, Eleventh Edition, 1910.
Zerubavel, pp. 45-46.
]. Article "Week," Encyclopedia Americana, 1963 edition.
Jeremy Campbell, Winston Churchill's Afternoon Nap, (New York: Simon and Schuster, 1986), pp. 77-78.
Zerubavel, p. 19.
Zerubavel, p. 20.
Zerubavel, pp. 25-26.
"The Seven-Day Wars" is Zerubavel's chapter two title, p. 27.
R. R. Palmer, The World of The French Revolution, (New York: Harper & Row, 1971), p. 120.
Zerubavel, p. 29.
Zerubavel, p. 43.
Susan Perry and Jim Dawson, The Secrets Our Body Clocks Reveal, (New York: Rawson Associates, 1988), pp. 20-21 (emphasis added).
Campbell, p. 79 (emphasis added).
Franz Halberg, "Quo Vadis Basic and Clinical Chronobiology: Promise for Health Maintenance," American Journal of Anatomy 168:543-594 (1983), p. 545.
Perry and Dawson, p. 8.
Perry and Dawson, pp. 8-9
Perry and Dawson, pp. 11-13.
Jeremy Campbell, p. 75.
Halberg, pp. 569-570; Campbell, pp. 75-76.

[22]. Eviatar Zerubavel, The Seven-Day Circle (Chicago: Univ. of Chicago Press, 1985), p. 11.
[23]. Jeremy Campbell, Winston Churchill's Afternoon Nap, (New York: Simon and Schuster, 1986). p. 83
[24]. Campbell, p. 15.
[25]. Campbell, p. 79.
[26]. Campbell, p. 133: emphasis added.
[27]. Susan Perry and Jim Davson, The Secrets Our Body Clocks Reveal, (New York: Rawson Associates, 1988) p. 22.
[28]. Campbell, p 76.
[29]. Franz Halberg, "Quo Vadis Basic and Clinical Chronobiology: Promise for Health Maintenance," American Journal of Anatomy 168:543-594 (1983), pp. 569-570.
[30]. Campbell, p. 132.
[31]. Campbell, p. 130.
[32]. Stephen W. Havking, A Brief History of Time (Toronto: Bantam Books, 1988), p. 8, emphasis ours.
[33]. Note the important switch from "one" to "second;" see commentaries.
[34]. Lev. 25:2-6.
[35]. Lev. 25:8.
[36]. Ex. 12:15, 19; Num. 29:12.
[37]. Lev. 23:23-25.
[38]. Lev. 16; 23; Zech. 14:16.
[39]. Lev. 4:6; Num 28:11; Lev. 14:7.
[40]. 2Kings 5:10.
[41]. Josh. 6:4, 1Kings18:43.
[42]. Mark 8:1-9.
[43]. Luke 10; Gen. 10:1.
[44]. Dan 9:24-27.
[45]. Desmond Ford, The Forgotten Day, [Newcastle, CA: Desmond Ford Publications, 1981) p. 7.
[46]. Ibid.
[47]. Isaiah 11:9, 66:22-23.
[48]. For a historical invenstigation into how early Christianity--not Christ or the Apostles--replaced a Saturday Sabbath (the seventh-day) with a Sunday "Sabbath" (the first day of the week) see Samuele Bacchiocchi's excellent work From Sabbath To Sunday (Rome: The Pontifical Gregorian University Press, 1977).
[49]. Hawking, p. 140-141, emphasis ours.

Written by: Ken Westby

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