For how long has the 7 day weekly cycle been unbroken?

Where are you, and how are you determining what day it is? If you’re in Samoa, and you use the local calendar, you could only go back as far as 2011. They went from a Thursday straight to Saturday. The poor Seventh Day Adventists had a schism over it.

Here in Panama working a half day on Saturday is still normal in many jobs.

My point is that Christians do not observe the Jewish Sabbath, but in fact worship on the day after the Sabbath. The unbroken seven day cycle discussed here specifically refers to the Judeo-Christian counting of days (Sunday to Saturday, being one to seven).

The change of the day of worship was an explicit change made by the early Christian community and confirmed by one of the early Catholic popes (however some minor protestant groups claim it was due to a “double day” vaguely described in the Old Testament to avoid admitting they are worshiping on the day the pope ordered!).

Christians observe the same worship cycle as Jews, for the same reason. The fact that (most) Christians offset their actual day of observance from that adhered to by Jews is theologically insignificant.

Again, any day in the cycle can be the “first” or the “seventh.” Religious communities adhere to arbitrary standards about which is which to identify their communality, and for practical reasons. There is no magic that works on Saturday but not Sunday, or vice-versa.

My original comment was about the incorrect use of the word “Sabbath”. Implying that “Sunday” is the “Sabbath” would mean there was a discontinuity in the seven day cycle, which has never been documented to have occurred.

This comment is now about the incorrect use of the word “theological”. The Christians changed the day of worship specifically because it was theologically significant to them. They specifically wished to distinguish their New Testament worship from the Jewish Old Testament worship.

Reading about that a few months ago gave me a headache!

Granted that in a continuously repeating cycle (like the week) which day is “first” and which day is “seventh” is somewhat arbitrary; Christians didn’t start counting Sunday as the seventh day, they changed the day of worship from the seventh day to the first day. The Christian theological position and the Jewish theological position still agree that the day on which most Christian churches meet is the first day of the week, and the day on which Jews keep the Sabbath (and some Christian churches which call themselves “Seventh-Day” meet) is the seventh day of the week. (Without getting into that whole “in Jewish reckoning the day starts at the previous sunset” issue.) It’s the influence of the secular workweek and the two-day weekend that causes people nowadays to consider Monday the first day of the week (and therefore Sunday as the last day).

Some Christians do refer to Sunday as “the Christian Sabbath”, while also explicitly acknowledging a discontinuity, not in the seven-day cycle as such, but in which day in that cycle is considered the “Sabbath”. From the Westminister Confession of Faith, Chapter XXI, “Of Religious Worship, and the Sabbath Day” (Presbyterian):

This is correct. What is ironic is that the Presbyterians call it the “Sabbath” only because Saint Thomas Aquinas (a Catholic!) called it that.*

*Technically, in his theological writings, he considered the commandment of worship on the Sabbath to be a reflection of Natural Law, and that worship on Sunday fulfilled this fundamental requirement of human nature, though the commandment to worship on Saturday expired. There are many other theological opinions on this matter.

The desire to distinguish communities is a cultural factor, not a theological one. To my knowledge, the theological basis for a seven-day cycle is still understood by all Jewish and Christian parties to be symbolically (at least) grounded in six days of Creation plus seventh day of rest.

Are there any cultures that observe something other than a seven day week?

There are several mentioned in the Wikipedia article:

It’s not clear to what extent they are currently observed.