The weekly cycle has never been changed. The Jews then worshipped on the Sabbath and they still do today.
The Sabbath was calculated differently back then. The Jews always worshipped on the Sabbath and they still do. It's just a different calculation.
And the proof would be?
Jewish Encyclopedia, do you accept that?
The origin of the Sabbath, as well as the true meaning of the name, is uncertain. The earliest Biblical passages which mention it (Ex. xx. 10, xxxiv. 21; Deut. v. 14; Amos viii. 5) presuppose its previous existence, and analysis of all the references to it in the canon makes it plain that its observance was neither general nor altogether spontaneous in either pre-exilic or post-exilic Israel. It was probably originally connected in some manner with the cult of the moon, as indeed is suggested by the frequent mention of Sabbath and New-Moon festivals in the same sentence (Isa. i. 13; Amos viii. 5; H Kings iv. 23). The old Semites worshiped the moon and the stars (Hommel, "Der Gestirndienst der Alten Araber"). Nomads and shepherds, they regarded the night as benevolent, the day with its withering heat as malevolent. In this way the moon ("Sinai" = "moon ["sin"] mountain") became central in their pantheon. The moon, however, has four phases in approximately 28 days, and it seemingly comes to a standstill every seven days. Days on which the deity rested were considered taboo, or ill-omened. New work could not be begun, nor unfinished work continued, on such days. The original meaning of "Shabbat" conveys this idea (the derivation from "sheba'" is entirely untenable). If, as was done by Prof. Sayce (in his Hibbert Lectures) and by Jastrow (in "American Journal of Theology," April, 1898), it can be identified in the form "shabbaton" with the "Shabattum" of the Assyrian list of foreign words, which is defined as "um nuḥ libbi" = "day of propitiation" (Jensen, in "Sabbath-School Times," 1892), it is a synonym for "'Aẓeret" and means a day on which one's actions are restricted, because the deity has to be propitiated. If, with Toy (in "Jour. Bib. Lit." xviii. 194), it is assumed that the signification is "rest," or "season of rest" (from the verb "to rest," "to cease [from labor]"; though "divider" and "division of time" are likewise said to have been the original significations; comp. also Barth, "Nominalbildungen," and Lagarde, "Nominalbildung"), the day is so designated because, being taboo, it demands abstinence from work and other occupations. The Sabbath depending, in Israel's nomadic period, upon the observation of the phases of the moon, it could not, according to this view, be a fixed day.
Now, for your Bible lesson.
"And the LORD spake unto Moses and Aaron in the land of Egypt saying, This month shall be unto you the beginning of months: it shall be the first month of the year to you. Exodus 12,1
"And Moses wrote their goings out according to their journeys by the commandment of the LORD: and these are their journeys according to their goings out. And they departed from Rameses in the first month, on the fifteenth day of the first month; on the morrow after the passover the children of Israel went out with an high hand in the sight of all the Egyptians. Numbers 33, 1-3
Now, counting from the "New Moon", Passover the 14th is ALWAYS on the 6th "day" of the week. In the above Scripture the Children of Israel left Eqypt "on the morrow" or the next day after Passover.
Here is the simple math,
New Moon Day (1), Day 2, Day 3, Day 4, Day 5, Day 6, Day 7, Day 8, Day 9, Day 10, Day 11, Day 12, Day 13, Day 14 (Passover), Day 15 (Sabbath Day)
Day 1 (New Moon) and Day 14 (Passover) have been identified. We know from Deut 16,1 that God brought the Children out of Egypt "by night" the day after the Passover. We know that the New Moon day is the first day of the first month of the first year because God commanded the Hebrews to keep the Passover Lamb up to the 14th day of the first month then to kill it.
If you go back and look at the "simple math" you will see that the 15th day, by default, is the Sabbath. Counting back 7 days identifies the 8th day as also a Sabbath. Day 1 can't be the Sabbath because it's the first day, of the first month of the first year and there is never a time where the New Moon day is the Sabbath, it's impossible. Counting forward from the 15th day we can identify the 22nd and 29th day as Sabbath days as well. This is the first Biblical month. The second month is laid out identical.
On the 15th Day of the Second month of the Exodus from Egypt the Children complained to Moses. Notice what happens. God tells Moses on the 15th Day that He will rain bread from heaven and test the Children to see if they will walk in His law or not.
On Day 15 God instructs Moses what to instruct the Children. If you read Exodus 16 you will see on the evening of the "15th day of the month" God caused quail to blow into the camp of the Children of Israel and the next morning manna started to fall. Day 15 = The Sabbath, plus 16th day (1st day of manna), 17th day (2nd day of Manna), 18th day (3rd day of Manna), 19th day (4th day of Manna), 20th day (5th day of manna), 21st day (6th day of Manna) whereas the Children are to gather twice as much manna because on the 22 day there will be no manna because that day is the Sabbath day. The math works out the same way as it did from the Exodus of Egypt with the Sabbath being on the 8th, 15th, 22nd and 29th day from the New Moon. That's two months wereas the Sabbaths were on the identical days of the same Lunar Calendar.
Is there ever three months in a row in the Gregorian Calendar where the Sabbath falls on the exact same days? Of course not, because the Gregorian is a solar Calendar and does not count or start from the New Moon.
It's exactly as the Jewish Encyclopedia stated it to be: The Sabbath depending, in Israel's nomadic period, upon the observation of the phases of the moon, it could not, according to this view, be a fixed day
The only thing that changed in the changeover from the Julian to the Gregorian was the number of the day: Something like Tuesday the 12 was followed by Wednesday the 25th.
Yeah, I realize that. That's not the point.
The issue is not from the Julian to the Gregorian. The calculation changed from the ancient Hebrew calendar to the actual Julian.
You broght up the change from the Julian to the Gregorian, now you change it to a Jewish to Julian and yuou've offered no proof for this claim.
See above and re-produce two concurrent months with the sabbath falling on the identical days within the months on either a Julian or Gregorian Calendar.