Is our modern Saturday the Sabbath? A History of Calendar Change.

How can we be sure that the Saturday of our modern week is the original Sabbath of the Scriptures?

It is commonly believed that many calendar changes have taken place since the time of Yeshua. This is not true. There has been only one change. This change, from the Julian calendar to the Gregorian Calendar, had no effect whatsoever upon the order of the days of the week. Julius Caesar instituted the Julian Calendar in 46 BC. The month of July was named in honor of Julius. When Augustus Caesar succeeded Julius, he also wanted a
month named after himself, so he gave the month following July (originally Sextilis) the name of August. Since August only had 30 days, and Augustus considered himself as important as Julius, whose month of July had 31 days, Augustus took one day from February and added it to August. The changes made by Augustus did not affect the order of the days of the week.

The Julian Calendar remained unchanged for 1600 years. It made provision for a year of 365.25 mean solar days. But the year actually consists of 365.242195 days. Because of this slight discrepancy, as the centuries passed, the seasons began to shift. By 1582 AD this discrepancy had grown to ten days. In that year Pope Gregory XIII established a new calendar which corrected the discrepancy, and is known as the Gregorian Calendar.

Pope Gregory XIII omitted ten days following October 4, 1582. What would have been October 5 became October 15.

Spain, Portugal, and Italy abopted the new Gregorian Calendar at once.  France waited until December, and it adopted the change by calling the 10th of December the 20th of December. The Catholic states of Germany adopted the calendar in 1583. The Protestant states of Germany did not adopt the new calendar until 1700. About the same time, Netherlands, Sweden, and Denmark adopted the new calendar. England adopted the calendar in 1752.

The Encyclopedia Britannica, 11th ed. vol. 4, p. 988, tells us:

The week is a period of seven days, having no reference whatever to the celestial motions--a circumstance to which it owes its unalterable uniformity... It has been employed from time immemorial in almost all eastern countries.

The Hebrew people spoke of the days of the week by number rather than by name. The only day that had a name was the seventh day which was called Shabat, the Sabbath, or the rest day. The day prior to the Sabbath was designated the preparation day. On this day, preparations were made for the family so that the Sabbath might truly be a day of rest for the entire family. All the days were numbered and spoken of in reference to the Sabbath. The first day was "first toward the Sabbath." The second day was "second toward the Sabbath, and so on. This was also the practice among the Syrians, Arabians, etc.  In at least 108 different languages the name for the seventh day, corresponding to our "Saturday", is a word meaning "rest day."

Can we be sure that the Sabbath has never been lost since Creation?  G-d sanctified the seventh day at Creation (Gen. 2:1-3). Even if the weekly Sabbath had been lost through the years, it was certainly re-established when G-d instructed the Israelites to not gather manna on Sabbath (Ex. 16:4). G-d later announced to the Israelites at Mount Sinai that keeping His Sabbath holy was part of His Ten Commandment law (Ex. 20:8-11). Since Mount Sinai the Jews have faithfully kept G-d's Sabbath, despite captivity, persecution, and dispersion, right down to our current day. Orthodox Jews, the Catholic church, Protestants, historians, and astronomers all agree with each other that there is no evidence that time has ever been lost. The same Sabbath that Yeshua and the apostles worshipped on (Luke 4:16,31; Acts 13:14-16,42,44) is the same seventh day Sabbath that Sabbath-keeping Christians worship on today… (By S. Berkowitz).

http://www.remnantofgod.org/7thdayneverchanged.htm