There is an apparently growing group of people that propose that weekly Saturday Sabbath keepers are in error, because calendar changes long ago in the dim past altered the weekly 7 day cycle, therefore the current week day cycle is erroneous. It is alleged that the correct Biblical weekly cycle can only be recovered by observing a lunar week, and thereby restore the observance of the correct weekly 7th day Sabbath.
Briefly, the lunar weekly Sabbath theory proposes the resetting of the month AND first day of the week with the new moon. That results in changing the day of the week being observed as the weekly Sabbath every month. Also under this theory, the weekly Sabbath always falls on the 8th, 15th, 22nd and 29th day of each month. In other words, that theory proposes that the weekly Sabbath actually floats to another day of the week at the new moon, and this happens every month.
The Bible does not teach that the week is set by the new moon. It teaches a 7 day week, as set once at creation, and that only the seventh day of the week is blessed and sanctified by God as a Sabbath day. There isn't a single example in the Bible of the first day of the week ever being determined or altered by the new moon, or that the weekly seventh day sabbath was ever changed since creation. There is also a complete absence of any historical evidence that Israel ever followed the alleged lunar weekly Sabbath. But this utter lack of any support for the theory does not deter those who are fascinated by it and promote it. It is much like those who think Sunday keeping can be proved from the Bible, or the secret pretribulation rapture, or the immortal soul, or infant baptism, etc., etc. Usually not even explicit scripture that contradicts their theory dissuades proponents of these erroneous teachings.
Since Christ is the creator God, He knew and kept the correct weekly Sabbath for the 33 years he was on Earth, as He was the author of it. Was it necessary for Him to correct the Jews on the weekly Sabbath they were then keeping? No. We can then conclude with certainty that from creation to the time of Christ the weekly Sabbath was correctly observed. Since then, the Jews have not relied on secular or Christian sources to adjust their weekly cycle.
That leaves only the period from 31 A.D. to the present to be examined for a change in the weekly 7 day cycle. By the second century the Catholic church in Rome was already into Sunday keeping, and that without making any calendar change. They have observed the first day of the week regularly without fail ever since then. The papacy has never altered the weekly 7 day cycle. The papal Gregorian calendar in 1582 went from Thursday, Oct. 4, to Friday, October 15. It skipped 10 days but did not change the week at all.
That leaves 31 A.D. to about 150 A.D. for the alleged calendar change. There are no historical documents from that time period where either the Catholic Church OR the Jews discussed changing the weekly cycle, and implemented this change since the time of Christ. No documentation of any such discussion exists, because it did not happen. There is absolutely no historical record of a calendar change that in any way altered the weekly cycle universally for the whole world since the time of Christ.