The Biblical Week Versus the Planetary Week

The Biblical Week Versus the Planetary Week

By Kelly McDonald, Jr.

Have you ever wondered where the names for the days of the week came from? Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday. None of these names are found in the Bible. The only day named by God was the Sabbath.

Did you know that the pagans in the first century had an alternative seven-day weekly cycle? It was based upon certain planets. For this reason, it has been called the planetary week. In this article, we will compare it to the Biblical week!

In the beginning of the Bible, we learn about creation and the establishment of the seven-day week. The first six days God created everything. On the seventh day, He rested. The day was blessed and set apart from the other six days.

Genesis 2:1-3 reads: “1 And the heavens and the earth were finished, and all the host of them. 2 And on the seventh day God finished his work which he had made; and he rested on the seventh day from all his work which he had made. 3 And God blessed the seventh day, and hallowed it; because that in it he rested from all his work which God had created and made” (ASV).

Knowledge of the seven-day weekly cycle continued after that time. It was understood in the days of Noah. This detail is explained in Genesis chapter 8.

“10 And he stayed yet other seven days; and again he sent forth the dove out of the ark; 11 and the dove came in to him at eventide; and, lo, in her mouth an olive-leaf plucked off: so Noah knew that the waters were abated from off the earth. 12 And he stayed yet other seven days, and sent forth the dove; and she returned not again unto him any more” (Gen 8:10-12, ASV).

Many years later, the children of Israel moved to Egypt where they were enslaved. During their captivity, they lost the knowledge of the Sabbath. Historical records show that the Egyptians had a ten-day weekly cycle (Fagan, 476). One of God’s first acts when they left Egypt was to re-establish the original creation week.

In Exodus chapter 16, we learn about a narrative familiar to many Jewish people and Christians – the story of the manna. What many people do not realize is that the main goal of the manna was to teach the Israelites which day of the week was the Sabbath. Through it, he restored to them the knowledge of the original seven-day cycle.

“4 Then said the LORD unto Moses, Behold, I will rain bread from heaven for you; and the people shall go out and gather a day’s portion every day, that I may prove them, whether they will walk in my law, or not. 5 And it shall come to pass on the sixth day, that they shall prepare that which they bring in, and it shall be twice as much as they gather daily.… 22 And it came to pass, that on the sixth day they gathered twice as much bread, two omers for each one: and all the rulers of the congregation came and told Moses. 23 And he said unto them, This is that which the LORD hath spoken, Tomorrow is a solemn rest, a holy sabbath unto the LORD: bake that which ye will bake, and boil that which ye will boil; and all that remaineth over lay up for you to be kept until the morning… 26 Six days ye shall gather it; but on the seventh day is the sabbath, in it there shall be none…’” (Ex. 16:4-5, 22-23, 26, ASV).

Notice in this passage that God never ascribed a name to any day of the week except the Sabbath. This is one practice that helped the children of Israel maintain the seven-day week through the centuries. The first six days of the week are as follows: first day, second day, third day, fourth day, fifth day, and sixth day. The seventh day of the week was named Sabbath or in Hebrew shabbat.

The Sabbath was one of the chief ways that time was reckoned in the Bible. This day is mentioned in dozens of verses in the Old Testament. It is the weekly regular of time (Ex. 20:8-11, 23:12, 2 Kings 11:5-9) and has special blessings for all people (Is. 56:1-7, 66:22-23).

Other days of the week only receive a sparse mention in the Bible. The first day of the week is inferred in the giving of the manna (Ex. 16:11-21). It is also alluded to in a few other verses (Lev. 23:11, 15-16). It is simply called “the day after the Sabbath.” In the New Testament, it receives several mentions. The sixth day is mentioned in the manna story (Ex. 16:5, 22, 29). There may be some other days of the week inferred from context of various Scriptures. However, the other days of the week are only referenced in relationship to the Sabbath (the weekly regulator).

By the first century AD, the Jewish people called the sixth day ‘preparation day’ because they prepared for the Sabbath on it. The earliest Christians seemed to continue this practice.

The Planetary Week

At some point in the centuries before Christ, another seven-day week developed in the Greco-Roman culture. Each day of this week was named after a heavenly body. It also had a different order than the Biblical week.

Some ancient cultures considered there to be seven planetes, which means wanderers in Greek. This is much different than our modern conception of a planet. They thought that the planets were stars because they could be seen in the night sky (Pliny, Natural History, 2.4; Cicero, The Republic, 6.17). These heavenly bodies also corresponded to deities that the Greeks and Romans worshiped.  

The names ascribed to each day of the week and their order were as follows:

Greek: Kronos, Helios, Selena, Aires, Hermes, Zeus, Aphrodite

Latin: Saturn, Sun, Moon, Mars, Mercury, Jove, Venus

Utilizing our modern vernacular, the planetary week was ordered to start with Saturday and end with Friday. Archaeological evidence has been found to confirm these details. Below, we will look at a few inscriptions pertaining to this subject.

Approximately mid-first century AD

In Pompeii, an inscription was found on a wall which listed the deities over each day in the planetary week. It was originally written in Greek and the heading of it reads: “Days of the gods.” It lists them in a specific order (original found in CIL 4: 5202). Below, we have provided the information from the inscription with the English translation in brackets.

THEON HAMERAS  [Days of the gods]

Kronou                        [Kronos]

Heliou                         [Helios]        

Selenes                        [Selena]

Areos                           [Aires]

Hermou                      [Hermes]

Dios                             [Zeus]

Aphrodeites                [Aphrodite]

Two more inscriptions were found near Pompeii. They showed the order of the days of the planetary week in Latin (CIL 4: 6779). I have placed the English translation beside them in brackets.

SATVRNI      [Saturn]

SOLIS            [Sol or Sun]

LVNAII          [Lunas or Moon]

MARTIS        [Mars]


IOVIS            [Jupiter or Jove]

VENERIS      [Venus]

(One name was missing from the original inscription: Mercury. This name is supplied by other findings).

The second inscription lists the days of the planetary week in short hand (Notizie degli Scavi, p 98 and CIL 4: 8863).

DIES    [Days]

SAT     [Saturn]

SOL     [Sol or Sun]

LVN     [Lunas or Moon]

MAR   [Mars]

MERC [Mercury]

IOV     [Jupiter or Iovi]

VEN    [Venus]

Christian Writings and the Planetary Week

Were early Christian writers in some way affected by the planetary week? If so, did it affect their theology? Below, we have listed some early Christian writings that discuss days of the week.

Didache (approx. 100 AD) – This ancient document mentions that the Jewish people fasted on the second and fifth days of the week. The author instructed fasting on the fourth day and the preparation day (chapter 8). No planetary names were used.

Epistle of Barnabas (130s AD) – This work referred to the Sabbath multiple times and the ‘eighth day’ in one chapter (chapter 15). No planetary names were used.

Justin the Martyr (150s AD) – In his work, Dialogue with Trypho, Justin mentioned the Sabbath multiple times. In chapter 41, he referred to the first day of the week which he also called the eighth day. In chapter 138, he mentioned the eighth day. In another work, Hortatory Address to the Greeks, Justin refers to the first day (chapter 33). In a third work, The Apology, Justin the Martyr possibly referenced the planetary names Saturday and Sunday. However, this reference contains inconsistencies; modern research shows that it is likely an interpolation. We will review this text in another article. Outside of this one spurious reference, Justin does not use the planetary names.

Theophilus of Antioch (160s-180s AD) – In his work To Autolycus, Theophilus discussed all the days of the week. He did not mention any planetary names.  He spoke very positively about the Sabbath and the Ten Commandments (idem, 3.9).

Clement of Alexandria was the first known Christian author to make an indisputable reference to the planetary week. He started writing in the late second century (180s). In Stromata, he wrote:  

“He knows also the enigmas of the fasting of those days — I mean the Fourth and the Preparation. For the one has its name from Hermes, and the other from Aphrodite. He fasts in his life, in respect of covetousness and voluptuousness, from which all the vices grow. For we have already often shown above the three kinds of fornication according to the apostle: love of pleasure, love of money and idolatry….He fasts, then, according to the law, from bad deeds, and according to the perfection of the gospel, from evil thoughts. He undergoes temptations, not for his purification, but as we have said, for the good of his neighbors…” (idem, 7.12; emphasis mine throughout).

He started this passage with the names for the days of the week that are used in the Bible – fourth day and the preparation. Some Christians were known to fast on these days, as the Didache indicates. He then acknowledged that these days of the week were commonly named after Hermes and Aphrodite (Latin: Mercury and Venus).

In another passage from the same work, Clement directly discussed the seven planets and the planetary week more in a more pronounced way:

“Now the high priest’s robe is the symbol of the world of sense. The seven planets are represented by the five stones and the two carbuncles, for Saturn and the Moon. The former is southern, and moist, and earthy, and heavy; the latter aerial, whence she is called by some Artemis, as if Aerotomos (cutting the air); and the air is cloudy. And cooperating as they did in the production of things here below, those that by Divine Providence are set over the planets are rightly represented as placed on the breast and shoulders; and by them was the work of creation, the first week. And the breast is the seat of the heart and soul” (ibid, 5.6; emphasis mine).

Clement tried to Christianize the seven planetes. He claimed that the high priests’ garment from the Old Testament was a foreshadowing of the seven planets. This is an allegorical interpretation of the Scriptures. He then tried to claim that the planetary names of the days of the week go back to the first week of creation in Genesis. Besides being archeologically and historically inaccurate, these claims are also far from Biblical.

Clement clearly had knowledge of the planetary week. He lived in Alexandria, Egypt; this city was heavily influenced by Greek culture. His knowledge on this subject is to be expected. He tried to merge the Biblical and Planetary weeks, though the orders were different. This was an attempt to syncretize or mix Christianity with other religions. Nothing in the Old Testament foreshadowed an alternative week than that given by God.

Tertullian, who wrote between 197-220 AD, discussed the Sabbath and Sunday using the planetary names for the days of the week. In the following two quotes, he made some unique statements that contribute to this topic.

“Others, with greater regard to good manners, it must be confessed, suppose that the sun is the god of the Christians, because it is a well-known fact that we pray towards the east, or because

we make Sunday a day (Latin: die solis) of festivity… It is you, at all events, who have even admitted the sun into the calendar of the week” (Against the Nations, 1.13).

“Others, again, certainly with more information and greater verisimilitude, believe that the sun (Latin: solem) is our god… In the same way, if we devote Sun-day (diem solis) to rejoicing, from a far different reason than Sun-worship…” (The Apology 1.16).

Tertullian is the first Christian writer to defend the faith from accusations of sun worship. This accusation came about through two practices: praying towards the sun and Sunday gatherings. He acknowledged that Sunday (or die solis) was celebrated by those who worship the sun. He also explained that the pagans added this day to the week (because the original seven-day week was not named after the planets).

Some later writers utilized the name Sunday as a theological justification for why they met on the day.  In his work In Die Dominica Paschae, Jerome (342-420) wrote: “If the pagans call it the ‘day of the sun’, we willingly agree, for today the light of the world is raised. Today is revealed the sun of justice with healing in his rays” (no. 1166, English Translation of the Cathechism of the Catholic Church for the United States of America. 1997, United States Catholic Conference, Inc.; Latin found in CCSL, 78:550).

As Christianity extended its influence into central and northern Europe, gods from those regions replaced four of their Greek/Roman counterparts in the planetary week: Tuesday (Tiw), Wednesday (Wooden or Odin), Thursday (Thor), and Friday (Frigga). The concept behind this revised terminology and where it came from remained the same.


The planetary week is much different than the Biblical week in two key ways. First, each planetary day was named for a heavenly body which corresponded to a god or goddess. On the other hand, the Biblical week only ascribed a name to the seventh day, the Sabbath. It is connected to the one true God resting on it. Secondly, the order for the days of the week was different. The planetary week started with Saturn-day and ends with Venus-day (modern usage: Saturday through Friday). The Biblical week starts with first day ends with Sabbath (modern usage: Sunday through Saturday).

For the first 140 years or so after the time of Jesus, references to the planetary week appear to be absent in Christian literature. Clement of Alexandria tried to Christianize the pagan names for the days of the week. He was likely the first to make these references and set the precedent continued by Tertullian and others.

His writings were part of a larger trend to syncretize Christianity with other religious influences. He tried this with other subjects, such as Greek philosophy. For the next two centuries, Christians in the West continued to use the planetary names for the days of the week on inscriptions such as gravestones.

In the West, the planetary week contributed to a decline in Sabbath observance. The use of the planetary name Sun-day in the West combined with a theological connection between Christ and the sun reinforced Sunday gatherings. On the other hand, the Sabbath has no linguistic connection to the planetary names for the days of the week.

In the East, the planetary week did not last as long. The Sabbath was also observed for a much longer period. Sabbaton was the common name for the seventh day of the week in the East, which allowed it to be reinforced both in name and in practice. Even in modern Greek, the terms preparation day and sabbath are retained in the words used for Friday and Saturday (paraskevi and savvato, respectively).

To learn more about the Biblical week, the Planetary week, and their impact on the Sabbath, download our free book How Did Sunday Become the First Day of the Week? (click here to download for free).

Kelly McDonald, Jr.

BSA President –


Cicero, M. Tullus. Of the Nature of the Gods. Translated by Thomas Francklin. London, 1829. pp 105-106.

Cicero, M. Tullus. The Republic. Translated by Francis Foster Barham and Charles Duke Yonge. Bohn’s Classical Library. London, 1878. pp 383-384.

Clement of Alexandria. Stromata, 5.6, 5.14, 7:12. Translated by William Wilson. Roberts, Rev. Alexander and Donaldson, James, eds. Revised by A. Cleveland Coxe. The Ante-Nicene Fathers. Vol. 2. Buffalo: Christian Literature Publishing Co, 1885. pp 453, 469, 544-545.

Corpus Inscriptorum Latinarum (CIL). 4: 5202, 6779, 8863.

Epistle of Barnabas. chapter 15. Translated by Alexander Roberts and James Donaldson. Roberts, Rev. Alexander and Donaldson, James, eds. Revised by A. Cleveland Coxe. The Ante-Nicene Fathers. Vol 1. Buffalo: Christian Literature Publishing Co, 1887. p 147

Fagan, Brian M. ed. The Oxford Companion to Archaeology. Vol. 1. 2nd ed. Oxford University Press. New York, 1996. p 476.

Holy Bible. American Standard Version (ASV).

Justin the Martyr. First Apology, 67. Dialogue with Trypho, chapters 41, 138. English. Translated by Marcus Dods and George Reith. Roberts, Rev. Alexander and Donaldson, James, eds. The Ante-Nicene Fathers. Revised by A. Cleveland Coxe. Vol. 1. Buffalo: Christian Literature Publishing Co, 1887. pp 187, 215.

Justin the Martyr. First Apology, 67. Latin. Patrologiae Cursus Completus. Series Graecae. Migne, JP. Vol. 6. Paris, 1857. pp 429-432.

Clement of Alexandria. Stromata, 1.5, 1.21, 6.14, 7.7. Translated by William Wilson. The Ante-Nicene Fathers. Edited by Rev. Alexander Roberts and James Donaldson. Vol. 2. Buffalo: Christian Literature Publishing Co., 1885, pp 305-306, 333, 505, 532-537.

Jerome. In Die Dominica Paschae. English: The Cathechism of the Catholic Church for the United States of America. 1997, United States Catholic Conference, Inc. Latin: CCSL, 78:550

Notizie degli Scavi Di Antichita.1927. Alla R. Accademia Nazionale Dei Lincei. Di S.E. il Ministro della Pubblica Istruzione. (V) Roma. Notizie degli Scavi, 26 April 1927. p 98.

Pliny the Elder. Natural History, 2.4. The Natural History of Pliny. Translated by John Bostock and H.T. Riley. Vol 1. London, 1855. pp 19-22.

Tertullian. Against the Nations, 1:13. English: Translated by Peter Holmes. Roberts, Rev. Alexander and Donaldson, James, eds. The AnteNicene Fathers. Vol. 3. Buffalo: Christian Literature Publishing Co, 1918. p 123.

 Tertullian. Against the Nations, 1.13, Apology, 1.16. Latin: Migne, Patrologiae Cursus. Completus. Series Latina. Vol. 1. Paris: 1844. pp 369-372, 579.

Tertullian. Apology 1.16. English: Translated by Rev. S. Thelwall. Roberts, Rev. Alexander and Donaldson, James, eds. The Ante-Nicene Fathers. Vol. 3. Buffalo: Christian Literature Publishing Co, 1918. p 31.

Theophilus. To Autolycus, 2.11-12, 15, 27. 3.9. Translated by Rev. Marcus Dods. Ante-Nicene Fathers, Vol 2. Roberts, Rev Alexander and Donaldson, James, eds. New York: Charles Scribner’s Sons, 1913. pp 99-101, 105, 113-114.

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