According to the international standard ISO 8601, Sunday is the seventh day of the week. However, many countries, including the US, Canada, and Japan, consider Sunday as the first day. Where does this contradiction come from and why does it matter if Sunday is the first or the seventh day of the week?
The origin of the week got lost in the mists of time, and the way in which it came into existence is the theme of various controversial theories. The placement of the week in the calendar is a special one, because it cannot be associated with any natural cyclical phenomenon (such as the day, month, or year), nor has it been present in all cultures, throughout history.
Still, why do we have a 7-day week now? The most widespread hypothesis was formulated by Jules Oppert, a renowned Assyriologist of the nineteenth century. Oppert discovered a list of Babylonian star deities, arranged in an order that corresponded to the days of the week: Shamash (Sun), Shin (Moon), Nergal (Mars), Nebo (Mercury), Merodah (Jupiter), Ishtar (Venus) and Adar (Saturn). Each hour of the day was assigned a protective god, and the star associated with the first hour of the day (sunrise) was considered the patron of the whole day: Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn, meaning exactly the order of the days of the week.
Both in ancient Mesopotamia and in classical Greco-Roman culture, the first day of the week was dedicated to the Sun and the last, to the god that was (sometimes) associated with death and darkness. This order would remain almost unchanged to this day.
Despite being the classical explanation, the hypothesis of the planetary origin of the week cannot answer a crucial question: Why did the Babylonians dedicate only seven days to gods? The number of Babylonian deities was much higher (15 main gods, from a total of over 30). Could the planetary model be just a Babylonian adaptation of an older model?
Another nation that played an important role in human history was the Jewish people. The Jewish religion and view of the world and life were unique in the ancient context. In the book of beginnings, the origin of the week is connected to the divine act of creation (see Genesis 1). Unlike the Mesopotamians, the Jews did not give names to the weekdays; they ordered them numerically, after the Sabbath; that is, the “day of rest” (the seventh day).
Most scholars of comparative religion believe that the Jews took the week from the Babylonians, along with the weekly Sabbath, the last day of the week dedicated to rest. However, Panbabylonism is a school of thought that seeks to attribute the evidence to other basic concepts. The similarities are always explained as a result of borrowing, but the possibility of a common source is not taken into account.
For example, while the Romanian word for Sunday is Duminica, and Italians say Domenica, the resemblance is not necessarily explained as a result of an import (of the Romanians from the Italians, or vice versa), but by taking into account a common source: Latin. Using the same logic, in the context of the discussion about the origin of the week, biblical accounts, along with Babylonian mythology, could indicate a pre-Babylonian origin of the week, a vestige of a primary monotheism, later adapted to polytheistic conceptions.
The seventh day of the week
In polytheistic cultures, there was no notion of a special day of the week to be set aside for worship. Each day represented a mixture of sacred and profane. In time, however, the pre-eminence of the worship of the Sun god caused the day associated with it to be treated with special consideration, thus becoming the first day.
The Jews, on the other hand, treated only one day of the week as sacred, namely the seventh. In the early days of Christianity, keeping the seventh day of the week was a part of the practice of Christians, whether they were of Jewish or pagan descent. There is no commandment of Jesus or the apostles to abandon the Sabbath and consider Sunday as a day of worship instead.
Historical evidence shows that the Sabbath continued to be a day of worship for more than 1,000 years after the death of Jesus, while the tendency to renunciate the seventh-day Sabbath was accentuated in the areas where there was a strong Solar cult (Alexandria and Rome). Adopting the first day of the week as a weekly day of worship for the Christian Church was a complex and lengthy process.
Anti-Jewish tendencies competed with the abandonment of worship on Saturday and the adoption of Sunday as a weekly Sabbath, after a long period of transition in which the two days were seen as “sisters.” An example of this is the expostulation of Gregory of Nyssa (c. 335—c. 395 C.E.): “How can you look upon the Lord’s day, if you neglect the Sabbath? Do you not know that they are sisters, and that in despising the one you affront the other?”
A collection of fourth-century church documents, called the Constitutions of the Holy Apostles (although researchers unanimously agree that the documents are not of apostolic origin), provides valuable information about the church’s worship, doctrine, and discipline at the time. The collection of documents is similar to a manual of internal order, in which the worship is confirmed on the seventh day (Sabbath) in parallel with the first day of the week (Sunday).
How Sunday became the new Christian Sabbath
In the fourth century, some Christians in the Phrygian area continued to abstain from work on the Sabbath, which was considered specific to the Jewish people. The Laodicean Synod acted against these “Judaizers,” warning believers to work on Sabbath and not to rest, like the Jews. Christians were urged to rest on Sunday in remembrance of the resurrection, “if it were possible” (si modo possum).
Later, a number of councils (synods) resumed the issue of “Sabbathisation”: The Council of Orléans (538), while protesting against excessive Sabbatarianism, banned any work in the field on Sunday. Subsequently, the Synod of Mâcon (585) established that the day of the Lord “is the day of perpetual rest, which is suggested to us by the type of the seventh day in the law and the prophets,” and a complete cessation of all kinds of affairs is commanded (not just agricultural ones).
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How far the pro-Sunday tendency had gone by the end of the sixth century is shown by a letter of Gregory the Great (pope between 590 and 604), which even forbade bathing on the first day of the week, often called “the day of the (resurrection of the) Lord.” Thus, Saturday was abandoned as a day of worship, and Sunday took over (at least partially) in the role of the Christian Sabbath.
Following a long and controversial history, the stance on the day of worship remains a highly disputed issue within Christianity. But one thing is clear: Sunday is the first day of the week, and Saturday is the seventh.