From the Creation to the Exodus
Let us suppose for the moment that the shabbath was "lost" sometime between the creation and the exodus. It absolutely was not, of course, for Yahuwah's laws were known and kept by faithful believers long before they were given to Yisra'el (Israel) at Mount Siynay (see B'ereshiyth [Genesis] 26:5) and the sacred calendar and weekly cycle was followed as far back as the days of Noach (B'ereshiyth 7:11, 8:9-14). Yet supposing that the shabbath had been lost we can be certain that it was identified and established again by the Almighty in the days of Mosheh (Moses).
Here is how we know this fact. In Shemot (Exodus) 16:14-30 we read of how the Almighty fed Yisra’el with manna. By the following three miracles - performed every week continuously for forty years - Yahuwah made known His shabbath day to the whole nation.
By these three distinct miracles which occurred every week for 40 years Yahuwah identified the seventh day as His Shabbath.
From the Exodus to the Apostolic Era
Was the identity of the seventh day "lost" between the exodus and the time of the Anointed Yahushua? The answer is - Absolutely not! But again, for the sake of argument, we'll assume that it was.
We can be certain that it was again identified when the Anointed observed it, for just prior to his death at Gulgoleth (Golgotha) the Savior categorically stated that He had kept his Father's commandments. (Yahuchanan [John] 15:10) He could hardly have said this if the day that He had been keeping for some thirty three years was the wrong one. Remember also that Yahushua was living in times that were under the dispensation of the Law of Mosheh! So if your argument is that the shabbath was under the "Old Testament" which was put aside at His death, then He had to obey the "Old" as it was still in force before that event. So if He had kept the wrong day He would have been a sinner and that would have disqualified Him from being our Savior.
We are, therefore, certain that the Savior kept the correct seventh day shabbath.
From the Apostolic Era to the Present Time
Has the identity of the seventh day of the week been "lost" over the past 1900 years? We can assure the reader that it hasn't been. Here is the proof.
Soon after the capture of Yeruwshalom (Jerusalem) in 70 CE the diaspora took place. The diaspora is the scattering of the body of Yahudiym (Jews) to lands other than their own. Initially the exiles had fled to the surrounding countries of Mitsrayim, Syria and Phoenicia, but in the course of time, as persecution mounted, the Yahudiym went further and further afield and today you will find Yahudiyth (Jewish) communities in every country on the face of the earth with the exception of many islamic states which have expelled them.
With them the Yahudiym took the Sacred Scriptures and their knowledge of the true shabbath day. Every seventh day since then orthodox Yahudiym all over the world have remembered the seventh day.
And what do we find in this 20th century? We find the Yahudiym still keeping the original seventh day shabbath, the same day they knew at the time of the diaspora, which was the same day Yahushua kept.
There is absolutely no disagreement or dispute amongst the Yahudiym - scattered as they still are - as to which day is the seventh day of the week. Every synagogue in every country is in perfect agreement that the seventh day is the shabbath, and that the scriptural seventh day starts at sundown on the secular weekday "Friday" and ends at sundown on the secular weekday "Saturday."
Had there been any change of the day, any loss or gain of time, any deliberate or accidental slip or alteration in the weekly cycle - which would have resulted in the Yahudiym in one country observing a different weekly shabbath from Yahudiyth believers in the next - then we would readily agree that the identity of the seventh day of the week was in doubt. But we do not find that situation anywhere on earth. Instead we have in total agreement amongst all the Yahudiym of all nations that the day known throughout the world as the shabbath is the seventh day of the week.
Some will argue that the civil calendar was changed in the sixteenth century and the weekly cycle itself was altered - all over the world - so no one can be certain which day is the true seventh day of the week.
Those who use this argument are misinformed. Here are the facts of history: In the year 1582 CE the Julian calendar (named after the Emperor Julius Caesar) was found to be 10 days late when compared with the position of the sun. That is, the vernal equinox was not occurring on or about March 20/21 - as it should do in a correct solar calendar - but was gradually receding towards the beginning of March. The reason for this error was that the Julian calendar worked on the basis that a year was 365¼ days in length, whereas in truth it is about 11 minutes more than that. Over the centuries this 11 minute discrepancy accumulated causing the Julian calendar to steadily recede until by the sixteenth century it had lost 10 days and the equinox was occurring on March 11th.
To correct this discrepancy Pope Gregory XIII ordered that 10 days be added to the Julian calendar dates to bring them into line with the sun. The month of October was chosen for the amendment and in the calendar of 1582 CE that month appeared as follows:
You will notice from the above that the weekly cycle, the order of the days of the week, remained unchanged even though the Gregorian calendar dates had increased by ten between the "Thursday" and the "Friday." In other words in both calendars the day after Thursday 4th was still a "Friday."
This amendment, understandably, was not very popular in some countries mainly because it had been organized by a Roman Catholic Pope. Several Protestant countries refused to acknowledge it and continued to use the Julian calendar, but one by one they came into line. Here is a short list of when they did:
Germany (Catholic States) 1583 CE
Germany (Protestant States) 1700 CE
Netherlands 1700 CE
England 1752 CE
Rumania, Turkey and Russia 1919 CE
All those years between 1582 CE and 1919 CE while both calendars were in use, the sequence of the days in the weekly cycle was the same in every country. In other words "Sunday" in Rome in 1900 CE was also Sunday in Russia in that year even though both countries were using a different calendar. And as each nation adopted the Georgian calendar it simply added 10 days to its Georgian Calendar date. There was no need to change the order of the days of the week, because they were already in agreement.
Related articles which you may find to be of interest.
Lunar Shabbath Refuted by Scripture
The Shabbath. Saturday?
The Shabbath Day of Yahuwah
When Does the Shabbath Start?
True Shabbath in the Languages of the World
The Shabbath Over the Centuries
Shabbath References in Scripture
Week Chart of the Shabbath