When was Sunday created?

I mean, we have Sunday once a week , so every 7 days, who decided that?

The same thing for Islam, who decided that the holy day is Friday, that happens to be every 7 days?

I looked it up and google says "321 CE Emperor Constantine" I don't know much about religion, so, if Jesus was born in year 0 (Emperor Constantine wasn't alive yet) then, was Sunday somehow related to the lunar calendar?

  • I think this is where the Emperor Constantine part comes from.
    – Peter Turner
    Commented Feb 3, 2022 at 4:56

3 Answers 3


And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
— Genesis 1:5

Biblical days run from sunset to sunset, rather than from midnight to midnight, but this "first day" of creation would be what we now call Sunday.

And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.
— Genesis 2:3

The seventh day, the sabbath, is from sunset on Friday to sunset on Saturday. There is no disagreement from Christian denominations that Saturday is the sabbath day of the Bible:

It was the Catholic church that declared that Sunday would be a solemn day for Christians, but they don't deny that the Bible designates Saturday as the Sabbath day:

The seventh day of the week among the Hebrews, the day being counted from sunset to sunset, that is, from Friday evening to Saturday evening.

But you may read the Bible from Genesis to Revelation, and you will not find a single line authorizing the sanctification of Sunday. The Scriptures enforce the religious observance of Saturday, a day which we never sanctify.
— James Cardinal Gibbons, The Faith of our Fathers.
Roman Catholic and Protestant Confessions about Sunday

Also, there was no "year 0"; 1 BC was immediately followed by AD 1 (they of course didn't use that terminology at the time).
And it's most likely Jesus was born in, or about, 4 BC.


God created the world in seven days, according to Genesis. Putting aside whether this is "literal" or "allegorical" and all of the debate around that, historically, the Jewish/Christian/Islamic calendars traditionally have 7 days because of this. The seventh day, as we can see in Genesis (in the creation narrative) and in Exodus (in the ten commandments), is the Sabbath, the day God rested. Jesus rose the day after the Sabbath, which would make that day the first day of the week. In English, we call the first day of the week "Sunday." Christians traditionally honor this day as the Sabbath as a sign of their having entered into the new covenant in Christ's blood (Luke 22:20) and our expectation that we will be resurrected with Him on the Last Day (Romans 6:4).


When was the first Sunday?

The term Sunday is derived from Egyptian astrology.

St. Justin (100-165) is the first Christian writer to call the day Sunday (I Apol., lxvii) in the celebrated passage in which he describes the worship offered by the early Christians on that day to God.

Sunday (Day of the Sun), as the name of the first day of the week, is derived from Egyptian astrology. The seven planets, known to us as Saturn, Jupiter, Mars, the Sun, Venus, Mercury, and the Moon, each had an hour of the day assigned to them, and the planet which was regent during the first hour of any day of the week gave its name to that day. During the first and second century the week of seven days was introduced into Rome from Egypt, and the Roman names of the planets were given to each successive day. The Teutonic nations seem to have adopted the week as a division of time from the Romans, but they changed the Roman names into those of corresponding Teutonic deities. Hence the dies Solis became Sunday (German, Sonntag). Sunday was the first day of the week according to the Jewish method of reckoning, but for Christians it began to take the place of the Jewish Sabbath in Apostolic times as the day set apart for the public and solemn worship of God. The practice of meeting together on the first day of the week for the celebration of the Eucharistic Sacrifice is indicated in Acts 20:7; 1 Corinthians 16:2; in Apocalypse 1:10, it is called the Lord's day. In the Didache (14) the injunction is given: "On the Lord's Day come together and break bread. And give thanks (offer the Eucharist), after confessing your sins that your sacrifice may be pure". St. Ignatius (Ep. ad Magnes. ix) speaks of Christians as "no longer observing the Sabbath, but living in the observance of the Lord's Day, on which also Our Life rose again". In the Epistle of Barnabas (xv) we read: "Wherefore, also, we keep the eighth day (i.e. the first of the week) with joyfulness, the day also on which Jesus rose again from the dead".

St. Justin is the first Christian writer to call the day Sunday (I Apol., lxvii) in the celebrated passage in which he describes the worship offered by the early Christians on that day to God. The fact that they met together and offered public worship on Sunday necessitated a certain rest from work on that day. However, Tertullian (202) is the first writer who expressly mentions the Sunday rest: "We, however (just as tradition has taught us), on the day of the Lord's Resurrection ought to guard not only against kneeling, but every posture and office of solicitude, deferring even our businesses lest we give any place to the devil" ("De orat.", xxiii; cf. "Ad nation.", I, xiii; "Apolog.", xvi).- Sunday

  • Could you elaborate on the source of Sunday from Egyptian astrology? Where did Justin M get the definition? In the bible, the first day (or 8th day) is the day after the Sabbath. All the days were related from that anchor. There is no "Sunday" in the bible (all versions but NLT).
    – SLM
    Commented Feb 4, 2022 at 18:37

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