# When did the current 7-day week cycle begin?

Today it's Sunday. 7 days ago it was Sunday. 7000 days ago it was Sunday. But what about 70,000 days ago, 700,000 days ago, and 7 million days ago? Our current 7-day week cycle has not continued unbroken forever. So my question is, when did our current 7-day week cycle begin? Note that I'm not asking when any 7-day week cycle was invented, but rather the specific cycle we're still on.

Here is what Wikipedia says:

The continuous seven-day cycle of the days of the week can be traced back to the reign of Augustus; the first identifiable date cited complete with day of the week is 6 February AD 60, identified as a "Sunday" (as viii idus Februarius dies solis "eighth day before the ides of February, day of the Sun") in a Pompeiian graffito. According to the currently-used Julian calendar, 6 February 60 was, however, a Wednesday. This is explained by the existence of two conventions of naming days of the weeks based on the planetary hours system: 6 February was a "Sunday" based on the sunset naming convention, and a "Wednesday" based on the sunrise naming convention.

So February 6, 60 AD is the earliest identifiable date with a day of the week cited with it, but this was based on sunset naming convention, rather than the sunrise naming convention we use today. So what is the earliest identifiable date with a day of the week cited with it that is based on the sunrise naming convention?

• "7000 days ago it was Sunday" This is possible, but if you have a source for it it would already be part of the answer I suppose. – Evargalo Oct 30 '17 at 8:54
• @DenisdeBernardy I want to know what is the largest value of x such that 7x days ago, it was considered (by someone or the other) to the same day of the week it is today. Today is Monday. What number of days which is a multiple of 7 can I go back in time where I'll find someone who will agree with me that it's Monday? – Keshav Srinivasan Oct 30 '17 at 12:42
• @Evargalo It's obvious. 7000 days ago is just 19 years ago. I don't know when our current 7-day week cycle began, but I'm sure it began earlier than 1998 :-) And any multiple of 7 days ago, as long it's after the current 7-day week cycle began, would be the same day of the week as it is today. So it should be clear that 7000 days ago it was the same day of the week as it is today. – Keshav Srinivasan Oct 30 '17 at 12:45
• The basque language (whose origin is still unknown) originally comprised only three week days: Astelehena, Asteartea, Asteazkena. We still preserve these days' names, to which at some moment in history the rest 4 days were added. So, I am looking forward to an answer. Just as curiosity, the meaning of the days are: - beginning of the week - middle of the week - end of the week – Mikel Urkia Oct 30 '17 at 14:09
• Years ago I asked on a different forum whether we could be sure the Sabbath of Jesus of Nazareth's time was a multiple of 7 days from the Sabbath observed by Judaism today. Everyone seemed to feel it was but no hard evidence was forthcoming. – TheMathemagician Oct 30 '17 at 15:38

Timothy is somewhat correct with identifying Babylon, however the Babylonians only borrowed the system. Most of our time keeping dates all the way back to ancient Sumeria (2600BC-ish?) and is mentioned in the epic of Gilgamesh.

Earliest we can trace it is between 2600BC and 3000BC.

• What's mentioned in the linked text are "seven day periods". It's not clear to me whether these were strung together to cover all of time. – Aaron Brick Apr 5 '19 at 4:15
• Yes, it seems there are two parts to this question. If different ancient civilizations were using 7 day weeks simultaneously (say), to what extent could they be interchanged meaningfully?... and, if as civilizations rose and fell, we assume the time system of the successor would be imposed on the vanquished, then it seems one system has eventually prevailed over all others, and is still with us today. Whose is it? – Agent Orange Feb 6 '20 at 16:37

Those who believe in the strict truth of the book of the Bible (I do not myself) would of course say it goes back to God's creation of the world, see Genesis Chapters 1 and 2

Most others say the week comes from Ancient Babylon, known directly from at least 500 BC but presumably older, if the Jewish religion absorbed it during the Captivity in Babylon which is thought to have ended 538 BC see:

https://www.timeanddate.com/calendar/days/7-days-week.html