It's not on the Gregorian Calendar
According to the Bible, neither Saturday nor Sunday is the Sabbath! The original calendar described in the Torah and used by Moses was based upon the phases of the Moon, not a continuous weekly cycle. This Lunar Calendar was used for all the feast days, including the weekly Sabbath.
Since the Biblical calendar is based on the moon, it does not correspond to the days of the modern Gregorian Calendar. For example, the Sabbath is not always on Saturday but could be on Wednesday one month, and Thursday the next.
This can have serious economic impacts, as people desiring to follow the Sabbath today according to the Biblical Lunar calendar will find themselves having to ask for days off during the standard Monday-to-Friday work week. This would be not just once or twice a year, but every week. Obviously, such a schedule will not be looked upon favorably by most employers and fellow employees.
The format of the Biblical Month.
The Biblical month starts with New Moon Day. It looks like this:
(NM = New Moon, W = Work day, S = Sabbath)
On this calendar, the Sabbaths are always in the same place: The 8th, 15th, 22nd, and 29th of the month. Of course they are 7 days apart, but the count starts every Lunar month.
The knowledge of the calendar has resurfaced after being ignored for over 1500 years. Careful reading of the Scriptures, together with detailed study of history reveal that the the calendar used over 2000 years ago is not the same as today. The historical research reveals that Rome was responsible for enforcing the change.
All Roads Lead to (and from) Rome
Since many people regard Rome to be the prophetic "Beast" of the Book of Revelation, and since the Sabbath is an issue both of worship and economics (regulating days of work and rest), this calendar change is a candidate for the ominous warning:
"And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name."
Coming Soon: A New World Calendar
Furthermore, there is a proposed change which will render even traditional Saturday observance incompatible with the business calendar. A new world calendar is proposed for the end of 2012. http://www.theworldcalendar.org This calendar is the obvious choice to promote a world economy by fixing many nuisances caused by the present calendar. Some features of the new calendar are:
Of course, 365.25 days is not evenly divisible by 7. But 364 is. So the world calendar will have a business year of 364 days, and the extra day, at the end of the year, will be a world holiday. It will not have a name other than "World Day". That is, it will not be a Saturday, or Sunday, or Monday; it will just be a special "World Day".
The only problem is that the seven day cycle would be broken. At the end of the first year, the day called "Sunday", for example, is really "Monday", according to the seven-day cycle. It gets off by one day per year, except on leap years, which gets off by two days. Therefore, neither a Lunar Calendar Sabbath or a continuous seven-day Saturday Sabbath will conveniently fit into the new calendar.
The Biblical Evidence
In the Bible, the only times a Sabbath is identified with a numerical date, it is only on the 8th, 15th, 22nd, or 29th. Likewise, when one of those dates is mentioned, it is always a Sabbath.
The Feasts are the Key to the Hebrew Calendar
The Biblical book of Leviticus, written by Moses, describes all of the Jewish feasts in Chapter 23. Most people are familiar with Passover, and the Day of Atonement (Yom Kippur). They are also aware that these feasts do not fall on the same day each year, since they are based upon the moon. However, few people notice that the weekly Sabbath is listed among the other Feasts:
" And the LORD spake unto Moses, saying,  Speak unto the children of Israel, and say unto them, Concerning the feasts of the LORD, which ye shall proclaim to be holy convocations, even these are my feasts.  Six days shall work be done: but the seventh day is the sabbath of rest, an holy convocation; ye shall do no work therein: it is the sabbath of the LORD in all your dwellings.  These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons.  In the fourteenth day of the first month at even is the LORD's passover.  And on the fifteenth day of the same month is the feast of unleavened bread unto the LORD: seven days ye must eat unleavened bread.  In the first day ye shall have an holy convocation: ye shall do no servile work therein.  But ye shall offer an offering made by fire unto the LORD seven days: in the seventh day is an holy convocation: ye shall do no servile work therein. ... [continues with the other feasts up to verse 44]"
There is no indication that a different calendar is used for the Sabbath as compared to the other feast days which are all grouped together in Leviticus 23. Notice that there is no provision in the scriptures for a situation when a feast day would "clash" with a weekly Sabbath, as happens today.
Because they are now using the mixed calendar, the Rabbis have developed "Rules of Postponement" to avoid a clash. For example, they don't want the Day of Atonement to be adjacent to a Sabbath. However, if a Lunar Sabbath is used, then the Day of Atonement is always five days from the Sabbath, and there is never a problem.
Even though the Bible has many details about the feasts, it is silent on "postponements". Why? Because Moses and the Prophets didn't use a mixed calendar, and so they didn't need them.
It can be seen that, by calculating the seventh day Sabbath in the same way as the feast days (from the beginning of the lunar month), there are no "clashes", nor is there a need to add an extra day. The very fact that these Rabbinical "Rules of Postponement" exist is the "smoking gun" that indicates that the Rabbis are not using the Scriptural Calendar for the seventh day Sabbath!
The Feast of Tabernacles is a seven-day feast, as stated six times in Leviticus 23:34-42. The feast begins on the 15th day of the month which is a Sabbath, lasts for seven days, and then the eighth day, the 22nd of the month is a Sabbath. Here's just two of the verses from Leviticus 23:
" The fifteenth day of this seventh month shall be the feast of tabernacles for seven days unto the LORD. ....  Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast unto the LORD seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath."
When most Jews celebrate this Feast today, two problems occur:
This is because they are using two incompatible calendars!
Two Versions in the Ten Commandments
Exodus chapter 20 lists the "Ten Commandments". But when Moses repeats the commandments in Deuteronomy chapter 5, there is something unusual.
"Remember the sabbath day, to keep it holy. ... For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it."
" Keep the sabbath day to sanctify it, as the LORD thy God hath commanded thee.  Six days thou shalt labour, and do all thy work:  But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work,... And remember that thou wast a servant in the land of Egypt, and that the LORD thy God brought thee out thence through a mighty hand and by a stretched out arm: therefore the LORD thy God commanded thee to keep the sabbath day."
So the Fourth commandment in Deuteronomy does not mention Creation at all as a reason for the Sabbath. Instead, it talks about the exodus from Egypt. When did the Almighty bring them out from Egypt with a mighty hand?
"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."
"Observe the month of Abib, and keep the passover unto the LORD thy God: for in the month of Abib the LORD thy God brought thee forth out of Egypt by night."
It is well known that they left Egypt on the Sabbath of Unleavened Bread, at night. People today teach that the Sabbath of Unleavened Bread is different from the seventh day Sabbath. But here they seem to be related, or even the same. They are linked by the Fourth Commandment as recorded in two different renderings.
The Israelites left Egypt on the day after Passover (the Sabbath of Unleavened Bread) and it was the "fifteenth day of the first month". (Passover is the fourteenth of the first month of the year.) When does the first month begin? It is the first new moon in the Spring. (All of the months in the Hebrew calendar start at the new moon.)
The Battle of Jericho
In the famous Battle of Jericho, the Israelites marched around Jericho for seven days, in offensive battle readiness, and attacked the city on the seventh day. Which of those seven days was the Sabbath? None of them! They started on the New Moon day, had a seven day march, and then rested on the eighth day of the month, which was the Sabbath. The "Book of Jasher", which is not in the Bible but is historically useful, even says the march started on the New Moon.
The Manna and the Quail
Exactly one lunar month after they left Egypt, the people congregated together on the fifteenth day of the month, and they took that opportunity to complain to Moses about the lack of food. The story is in Exodus 16.
It specifically said that the quails would come "at even", and that the bread would come the next "morning". The simplest explanation for this is that the day, the fifteenth of the month, was the Sabbath, and that the people were to wait until after sunset before gathering food.
The quail was given in the evening after the Sabbath had past. The manna was given on the mornings of all the workdays, and twice as much on the Preparation day (the day before the Sabbath).
On the third month the whole congregation assembled before the Almighty. When did this assembly occur? On the 15th day of the third month! They left Egypt on the 15th day of the first month, and they came to Sinai on the 15th day of the third month.
"In the third month, when the children of Israel were gone forth out of the land of Egypt, the same day came they into the wilderness of Sinai."
Jesus kept the Lunar Sabbath
Yeshua healed a blind man on the Sabbath, the 22nd day of the seventh month. John 7:2 says that it was the Feast of Tabernacles, and John 7:37 says that on the last great day of the seven day feast, Yeshua announced that he was the source of living water. Then in John 7:53 we read that everyone went home (for the night) and the next verse, John 8:1, says that Yeshua went to the Mount of Olives.
The next verse says that in the morning they all went to the temple. The actual healing and the reaction of the Pharisees is the subject of John chapter 9. Some people try to use this scripture to say that the Sabbath was on the 23rd. But this argument requires that the Feast of Tabernacles be eight days long, not seven days, as specified in Leviticus.
The Historical Evidence
The Julian Calendar
The modern calendar began in 46/45 BC, when Julius Caesar, in consultation with the astronomer Sosigenes of Alexandria, developed the Julian Calendar of 365.25 days. The big innovation was to separate the week from the lunar cycle and to make it a continuous cycle. It used an eight-day market week, with the days simply named "A,B,C,D,E,F,G,H". Certain types of events were allowed on certain days, called fasti.
By the time of the First Century AD, the seven-day week named after "gods" and "goddesses" of the solar-system was being used in Rome, and was starting to replace the eight-day week.
But the 7-day solar system week was:
1. Saturn's day (obvious in English) 2. Sun's day (obvious in English) 3. Moon's day (obvious in English) 4. Mars' day (Spanish: Martes, French: Mardi) 5. Mercury's day (Spanish: Miércoles, French: Mercredi) 6. Jupiter's day (Spanish: Jueves, French: Jeudi) 7. Venus' day (Spanish: Viernes, French: Vendredi)
So Saturn's day was the first day of the week. However, the Jews and Christians were not using that calendar until the time of Constantine. While it is generally known that Constantine enforced a "Sunday Law", in AD 321, a big assumption is that he just replaced one day with the day next to it. Was there more to it? Yes, he changed the entire calendar.
Constantine's Hybrid Calendar
In AD 321, Constantine created a big compromise. He blended the Hebrew idea of a seven day week with the Julian concept of a continuous weekly cycle, and added the veneration of the "Sun God" from Mithrasim to create the Roman calendar used today. He enforced his calendar upon the entire Roman Empire with military power.
Constantine and the Council of Nicaea in AD 325 replaced Passover with Easter. On the surface, that may not seem to be much of a change. But it's not just a matter of replacing one day with another. It's a completely different system of calendation, since Passover is not computed using a Julian calendar.
Because of these changes which were being enforced by persecutions across the Roman Empire, the Jewish Sanhedrin met for the last time around AD 350, and modified the calendar to the form used by most Jews today, in which the Sabbath is on Saturday, but the other Feast Days use a form of Lunar calendar.
The modern Gregorian Calendar
Later in history, Pope Gregory modified Constantine's calendar slightly in 1582. (This was to fix a problem caused by the fact that the year is not exactly 365.25 days long, but 11 minutes shorter.) Like Constantine, the motivating factor was the date of Easter. So the calendation system used today is Roman (Pagan and Papal), and the question of when the Sabbath occurs is very important to anyone who desires to follow the Bible.
Did you know that Karaite Jews, an almost extinct and controversial sect, have always used the sighting of the New Moon, not the erroneous fixed calendar, to determine months and holidays? Despite centuries of concerted efforts toward eradication by assimilation, Karaim still practice Jewish tradition according to the Torah, unadulterated by early social reforms which generalized religious practice. Karaim believe in scriptural interpretation without distortion of context. Karaite views regarding the role of spiritual women, shaving, and tattooing also differ from what has become mainstream Judaism. There is a good explanation on karaite-korner.org.
Anyone interested in truth versus dogma, cultural preservation of a rich heritage, and all Jewish women should investigate this.
This is the best explanation on the Sabbath Day that I have ever seen. I have tried for decades (using the Gregorian Calendar of course) to covert the Sabbath, and wrap my mind around a simple understanding of the days. Now my little inner voice is telling me; "It's the Moon Stupid!", but I find that reading on about how most everyone else didn't get it either is somewhat comforting. And doing further research on this article yielded even
more: "In Babylonia... the goddess of spring was called Ishtar. She was identified with the planet Venus, which, because... [it] rises before the Sun... or sets after it... appears to love the light [this means Venus loves the sun-god]... In Phoenecia, she became Astarte; in Greece, Eostre [related to the Greek word Eos: "dawn"], and in Germany, Ostara [this comes from the German word Ost: "east," which is the direction of dawn]" (Englehart, p. 4).
It's amazing to see just how evil, and twisted it has all become through the centuries. And by the very people that we thought were telling us right, only to find that many of them, in all fairness, just had the wool pulled over their eyes as well.
Great article ViewZone, Thanks