I will explain the following:
1) When does a day start? By this, will it also show us when Sabbath day starts?
2) Who changed the weekly Sabbath from the inceptive morning, to inceptive evening?
To determine the beginning of an actual day, or should I say, when the day starts, it is best that we start in the beginning, Genesis 1, where Abba first started creating. The scriptures are clear, in verse 2, that darkness was over the face of the deep. In bigger essence, darkness covered the whole world. Then in verse 3, Abba said,"Let there be light." This darkness that covered everything has now been pushed in one place so that light can occupy it's space. According to science, two substances cannot occupy the same spot at the same time, thus, you cannot start evening as the beginning of the day within a 24 hour period. Day has to end before evening comes, and evening has to end before night comes. Understand this: It is only the end of the light that brings forth the evening/night.
Verses 4-5 shows us that Abba separated the light from the darkness, the day from the night. Then, it came to be evening, and it came to be morning, day one. Now, notice the last part..... evening, then morning.... day one. But, where's the previous morning before the evening, and the previous night before the morning of the next day? Logically, for the evening to "come to be", there had to have been a previous morning. Before there was a night, there had to have been a previous evening. So, as we can see, Abba has put in place, when one think's about it, morning, evening, and night. Even if things are stated indirectly, within the entire context, it's all there.
It would be impossible to simply look at a day by observing evening to morning only. That's not a 24 hour period. That's only about 13 hours, which severly falls short of the whole of the day. It falls short because it misses a day, and it misses a night. The only morning it mentions is the morning of the following day, and not the morning of the previous day. There needs to be a morning of a previous day, and the inclusion of the night, after the evening, for a complete day, 24 hours, to be over. There's a fact, that no where in scripture, will you get the completion of a day, less than 24 hours.
Noted Hebrew scholar, C. H. Leupold (Exposition of Genesis, Vol. 1, pp. 57-58) explains:
The verse [Gen. 1:5], however, presents not an addition of items but the conclusion of a progression. On this day there had been the creation of heaven and earth in the rough, then the creation of light, the approval of light, the separation of day and night. Now with evening the divine activities ceased: they are works of light not works of darkness. The evening (‘erebh), of course, merges into night, and the night terminates with morning. But by the time morning is reached, the first day is concluded, as the account says succinctly, ‘the first day,’ and everything is in readiness for the second day’s task. For ‘evening’ marks the conclusion of the day, and ‘morning’ marks the conclusion of the night. It is these conclusions, which terminate the preceding, that are to be made prominent."
While the evening marks the conclusion of the day, this does not, in anyway, mark the beginning of the following day. The beginning of the evening simply marks the removal of light, and now twilight has begun. Nothing more... nothing less. The actual whole of the day has not concluded with the arrival of the evening, and you shall see more of this evidence as you read on.
I would like to add a small piece here. Genesis 1:14-18,"And God said, “Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years, and let them be lights in the expanse of the heavens to give light upon the earth.” And it was so. And God made the two great lights—the greater light to rule the day and the lesser light to rule the night—and the stars. And God set them in the expanse of the heavens to give light on the earth, to rule over the day and over the night, and to separate the light from the darkness."
The Light that rules the day is the sun, and the lights that rule the night are the moon and stars. Now, the moon does not give light from itself, because the moon is a reflector of light, and it is not a star. Nevertheless, we do not need the sun to tell the day, and we do not need the moon or stars to tell the night. Simply stated, these are simply greater lights.. nothing more, and nothing less. It could be cloudy outside with no sunlight, and yet, there's light. It can be dark/night outside with no stars and moon, and yet, there's dark/night. Abba created light before He created the sun, and He created night before He created the moon and stars. Genesis 1:4-5,"And God separated the light from the darkness. God called the light Day, and the darkness he called Night."
In agreement with scripture, as stated previously, you cannot conclude to evening without establishing, first, the previous morning, and you cannot conclude to the morning without establishing, first, the previous night and evening. Notice this interesting statement in C.H. Leupold's quote,"Now with evening the divine activities ceased." If you go back to the beginning of verse 1-4, you will see that Abba is working(creating), during the day period, then He brings it to a close in the evening, and then morning comes, and this morning of the next day, ends the previous day(24 hour period).
Now watch this, notice verse 6. It uses the conjunction "and", to tell us that Abba has started creating in this morning, which is the next day. It says,"And God said." Again, this says that Abba begin to create on the morning of this day. Abba created the firmament in the midst of the water, and the sky. THEN, it came to be evening, then morning... the second day, which means that this second day has now ended by the morning of the next day.`
Highly esteemed Professor of Old Testament at Westminster Theological Seminary, Edward J. Young (Studies in Genesis One, p. 89) summarizes the Hebrew text as follows:
When the light was removed by the appearance of darkness, it was evening, and the coming of light brought morning, the completion of a day. The days therefore, are to be reckoned from morning to morning. . . .
From this evidence, we must conclude that since a new day began on the morning of each of the six days of creation week, It would make sense that Abba set apart His Sabbath on the morning of the seventh day.
Examples Of The Beginning Of The Sabbath, And Proving The Sabbath Day As Starting At Morning
We all know the story of the passover. Passover starts the beginning of months. Abba commanded that on the 10th of this month, we must take a 1 year old, perfect sheep. It shall be kept for us until the 14th of this month. And the sons of Israel shall slay towards the evening. Some translations render this,"at twilight, or in the evening."Basically, towards evening, going on night, they were to slaughter the sheep.
Some hold that this evening actually begins the new day, and they are to slaughter at the evening, but this conflicts with the whole of the text. The text says that on the 14th day of this month, towards evening, for which the day(removal of light) had to have passed for evening to come. According to the text, we're still on the 14th, and the evening has not started the 15th. The killing and the eating of the sheep were to be done on the 14th day, and the 15th day has yet to arrive. Verse 8 says that they shall eat the meat that same night/this night, which is on the 14th. The 15th day has yet to arrive, by the arrival of the morning. Verse 10 says that they shall not leave any leftovers until morning.
On the night of the 14th, Abba will strike the firstborn of Egypt. He will do it by the night. Abba said,"this night." Some translations say,"that night." Nevertheless, the context shows us that we're still on the 14th, and not the start of a new day, the 15th. Thus, again, this shows us that a day does not start in the evening. Abba says,"This day(the 14th) shall be a memorial for you." For the evening to have started a new day, Abba would have had the slaughtering of the sheep done on the 13th day, before sunset, and then on the 14th day, at sunset, they were to eat the sheep. But the context says no such thing.
Interesting enough, the feast of unleavened bread was to be done on the same day, the 14th. Israel was to eat this bread for 7 days, from the 1st day until the 7th day. On the 7th day, no service work is to be done. Now let's look carefully at verse 18, for it says,"When the 1st month begins on the 14th day, from the evening you shall eat unleavened bread until the 21st day of the month until the evening." My question to you is,"If a day starts at evening, then why didn't Abba say,"On the 15th day, from the evening? Obviously, a day does not start at evening, but in the morning, as we shall see.
Exodus 16: The Manna & The Sabbath:
This is one of the great scriptures, among many, that proves that the Sabbath starts in the morning. It shows us that Abba wants His people to gather manna on the morning of the 6th day, because on the 7th day, in the morning, they will not find it there. Verse 21,"They gathered it morning by morning." Notice that it did not say,"They gathered it evening by evening." In Israelite culture, work is not done in the evening.. not because its a Sabbath, or that it begins a new day, but that work is not done in the evening.. similar to the creation story, where Abba does no work in evening, but only during the day.
So, the Israelites were not to leave any manna until morning. At evening, quails came and covered the camp, and in the morning, there was a layer of dew around the camp. Verse 12 says,"'At twilight you shall eat meat, and in the morning you shall be filled with bread." Verse 22,"Now on the sixth day
they gathered twice as much bread, two omers for each one When all the leaders of the congregation came and told Moses."
As you'd agree, they did their gatherings only in the morning, and ceased it in the evening, for they were to eat in the evening.
Notice Moses' words here in verse 25,"This is what the LORD meant: Tomorrow is a sabbath observance, a holy sabbath to the LORD. Bake what you will bake and boil what you will boil, and all that is left over put aside to be kept until morning."
Why did Moses say,"Tomorrow is a Sabbath, if the Sabbath day started in the evening of the 6th day? He could have said," Today, at evening is a Sabbath." Obviously, the evening is the winding down of the 6th day, and not the end of the 6th day. Verse 1 says,"This will happen when the LORD gives you meat to eat in the evening, and bread to the full in the morning." In the morning, on the Sabbath day, they were not to leave their homes to look for manna in the field, because there would not be any in the field. Whatever they laid aside for the morning, were to be eaten in the morning, on the Sabbath.
Verse 23,"Moses said, "Eat it today, for today is a sabbath to the LORD; today you will not find it in the field." Baked and boiled things were kept aside til morning, and in that morning, Moses told them to eat it, because today is a Sabbath. From the context, the day started in the morning, and no bread would be in the field on the Sabbath day. Thus, proves to us that a day starts in the morning, and so does the Sabbath day.
Here Is The Sequence To This Whole Matter:
1) The 6th day, when they prepare what they bring in, it will be twice as much as they gather daily.
A) At evening you shall know that it was the Lord who brought you out of the land of Egypt, and in the morning you shall see the glory of the Lord.
B) When the Lord gives you in the evening meat to eat and in the morning bread to the full.
C) At twilight you shall eat meat, and in the morning you shall be filled with bread.
D) In the evening quail came up and covered the camp, and in the morning dew lay around the camp.
E) Tomorrow is a day of solemn rest, a holy Sabbath to the Lord; bake what you will bake and boil what you will boil, and all that is left over lay aside to be kept till the morning.
2) The 7th day
A) So they laid it aside till the morning.
B) Eat it today, for today is a Sabbath to the Lord; today you will not find it in the field.
C) Six days you shall gather it, but on the seventh day, which is a Sabbath, there will be none.
D) On the seventh day some of the people went out to gather, but they found none.
See the evidence that the Sabbath starts in the morning? I sure do! At evening, it is still the 6th day, but in the morning, the Sabbath has dawned.
The Day Of Preparation(Matthew 27:57-62; Mark 15:42-46; Luke 23:50-54; John 19:38-42):
Let's look at the following verses here:
Matthew 27:57-62,"When it was evening, there came a rich man from Arimathea, named Joseph, who himself had also become a disciple of Jesus."
Verse 62,"Now on the next day, the day after the preparation, the chief priests and the Pharisees gathered together with Pilate."
Mark 15:42,"When evening had already come, because it was the preparation day, that is, the day before the Sabbath."
Luke 23:54,"It was the preparation day, and the Sabbath was about to begin."
John 19:42,"Therefore because of the Jewish day of preparation, since the tomb was nearby, they laid Jesus there."
From the above New Testament scriptures, we have proof that the Sabbath starts in the morning, and not in the evening. Notice Mark 15:42. Evening came, which would be a friday, and this day, according to the text here, is the day before the Sabbath. According to sunset Sabbatarians, the Sabbath should have started in that evening, the day of preparation, but it looks like scripture clearly refutes that. If the Sabbath actually started in the evening before the actual 7th day, then Jesus would have been laid in the tomb on the Sabbath(that friday evening), and that is against Jewish custom. Jesus was laid in the tomb, according to scripture, the day before the Sabbath.
Let us look at this scripture here. Deuteronomy 21:23,"his body shall not remain all night on the tree, but you shall bury him the same day." This is all the more proof that Jesus could not have stayed on that cross all night, before the Sabbath. He had to be prepared to be buried the same day He died. All this is inline with the evidence, of the fact, that a day does not start at evening, but starts in the morning.
Here's Some Historical Quotations Of When A Sabbath Day Begins:
Rabbinic tradition on this subject is in fact mixed. Harold Hoehner demonstrates from the Mishnah that there were actually two systems of reckoning a day at the time of Christ.
The Galileans and Pharisees used the sunrise-to-sunrise reckoning whereas the Judeans and Sadducees used the sunset-to-sunset reckoning. . . . This view not only satisfies the data of the Synoptics and the Gospel of John, it is also substantiated by the Mishnah. It was the custom of the Galileans to do no work on the day of the Passover while the Judeans worked until midday [the footnote reference is to Mishnah : Pesahim iv.5]. Since the Galileans’ day began at sunrise they would do no work on the entire day of the Passover. On the other hand the Judeans’ day began at sunset and they would work the morning but not the afternoon" (Chronological Aspects of the Life of Christ, p.87,88).
William S. Plumer, a nineteenth century Southern Presbyterian minister wrote the following in an exposition of the ten commandments entitled, The Law of God, as Contained in the Ten Commandments, Explained and Enforced (Presbyterian Board of Publication, 1864, pp.309-310):
When does the Sabbath begin?
There is some diversity in the Christian world respecting the time, at which the Sabbath begins. Some date it from sunset on Saturday till sunset on Sabbath. When asked for their authority, they refer to a phrase which occurs several times in the first chapter of Genesis: "And the evening and the morning were the first day." This has not been considered sufficient proof by the great mass of the Christian world. Nor ought it to be, as all the world knows that no day of creation began in the evening; but all of them began in the morning. That saying of Moses therefore only declares that the day was made up of two parts, the after part, and the fore part. Indeed the evidence in the New Testament seems to be clearly against this view. "Our Sabbath begins where the Jewish Sabbath ended; but the Jewish Sabbath did not end towards the evening, but towards the morning. Matt. 28:1. ‘In the end of the Sabbath, as it began to dawn towards the first day of the week,’ etc. In the New Testament, the evening following, and not going before this first day of the week, is called the evening of the first day, John 20:19. ‘The same day, at evening, being the first day of the week,’ etc. Our Sabbath is held in memory of Christ’s resurrection, and it is certain that Christ rose early in the morning of the first day of the week."
I believe that I have established much ground here, although there's more evidence to be proven. There are more things that needs to be dealt with, and that is the day of atonement. Let's look at the day of atonement. This is the only time where an evening to evening Sabbath is commanded. Lev 23:27,"On exactly the tenth day of this seventh month is the day of atonement; it shall be a holy convocation for you, and you shall humble your souls and present an offering by fire to the LORD." Verse 32 says,"It is to be a sabbath of complete rest to you, and you shall humble your souls; on the ninth of the month at evening, from evening until evening you shall keep your sabbath."
On the 10th day of this seventh month, during the day of atonement, at evening, from evening to evening. As evident, evening cannot come without a morning, and so the actual day of the 10th started in the morning. But, at evening, we're to begin our Sabbath. This is the only evidence of an sunset Sabbath that sunset Sabbatarians use, and try to fit it into every Sabbath, including the weekly Sabbath, but other scriptures, and mainly context, as evident from above, forbids this.
Who Changed Thought Patterns Of When The Weekly Sabbath Begins? Are You Really Following The Rabbis, Or Scripture?:
Here is an excerpt from a book showing how Rabbinic Judaism has even changed when the day and therefore the Sabbath begins. My family observes Sabbath from sunrise to sunrise (Saturday sunrise to Sunday sunrise.)
RABBINICAL ESSAYS BY JACOB Z. LAUTERBACH HEBREW UNION COLLEGE PRESS CINCINNATI 1951 From page 446 - 451 with notes
Before we proceed to describe the ceremonies of the entrance of the Sabbath we must ascertain the exact time of her appearance, that is, at what time of the day the arrival of the Princess Sabbath was expected. This will help us to understand better certain features in the arrangements for welcoming her. As the Sabbath is the seventh day of the week and extends over one whole day, a brief discussion of the development of the Jewish system of reckoning the day is necessary to determine the time of the coming in and the going out of the Sabbath. There can be no doubt that in pre-exilic times the Israelites reckoned the day from morning to morning. The day began with the dawn and closed with the end of the night following it, i.e, with the last moment before the dawn of the next morning. The very description of the extent of the day in the biblical account of creation as given in Gen 1.5 presupposes such a system of reckoning the day, for it says: "And it was evening and it was morning, one day."
This passage was misunderstood by the Talmud, though significantly enough when the Tosefta cites in proof Esth. 4.16 where the order occurs, but does not cite the passage in Genesis or was reinterpreted to suit the later practice of a different system. But it was correctly interpreted by R. Samuel b. Meir (1100-1160) when he remarked "It does not say that it was night time and it was day time which made one day; but it says 'it was evening,' which means that the period of the day time came to an end and the light disappeared. And when it says 'it was morning,' it means that the period of the night time came to an end and the morning dawned. Then one whole day was completed." There are many more indications in the Pentateuch pointing directly or indirectly to the mode of reckoning the day from morning to morning.
To mention but a few such indications; when prescribing that a Thanksgiving offering must be consumed on the very same day on which the sacrifice is slaughtered, the Law states "on the same day it shall be eaten, ye shall leave none of it till the morning"  which directly indicates that the day comes to an end on the next morning. And when in special case, as e, g., in regard to the Day of Atonement, where the Law wishes to make the fasting on it stricter than on any other fast day so as to include also the preceding night, the Law specifically states that it should begin with part of the preceding day and therefore expressly says: "And ye shall afflict your souls in the ninth day of the month at even, from even to even shall ye keep your Sabbath." [54 ] This indirectly but unmistakably points to a mode of reckoning the day from morning to morning. In post-exilic times, however, probably not later than the beginning of the Greek period,  a change in the system of reckoning the day was made, and the day was reckoned as extending from the preceding to the following evening. As might be expected, such a radical innovation was not immediately generally accepted It took some time before it entirely supplanted the older system. In certain spheres of the population the older system continued to be in use, either exclusively or side by side with the newer system.
Thus in the Temple service the older system continued all through the time of the existence of the second Temple, and there the day was reckoned from morning to morning, or as the Talmud  puts it [Hebrew quoted] "In sacrificial matters the night follows rather than precedes the day."  " In some circles  or among some Jewish sects  the older system continued and the Sabbath was observed from Saturday morning to Sunday morning For those groups, as for the people of the time prior to the introduction of the new system, the night following the Sabbath and not the night preceding it formed part of the Sabbath, and the morning of Saturday -- not Friday evening -- marked the entrance of the Sabbath.· But the majority of the people, following the teachings of the Halakah.  reckoned the day from evening to evening and the entrance of the Sabbath for them came after the sunset of Friday or on Friday evening. All the arrangements for welcoming the Sabbath and the ceremonies connected with it were set for Friday evening.
We must conclude, from the above evidence, that the weekly Sabbath day cannot begin at evening, but, like the regular day, begin at morning. We must conclude that it isn't scripture that reckons a day, or the weekly Sabbath, evening to evening. It is the Rabbis that reckons a day as such. The only evidence we see in the change of Sabbath observance, is not in the weekly Sabbath, but in the high Sabbath, in the day of atonement. That's about it! I would also like to add that, when the day is over, and evening arises, this does not conclude the whole of the day, but only, the removal of the light. If today is the 14th, then evening does not conclude the 14th, and it's now the 15th.
The evening is still the 14th, and the 15th begins in the coming morning. Let us live off the word of Abba, come out of Babylon, and leave the traditions of man alone. Jesus said in Mark 7:7-8,"In vain do they worship me, teaching as doctrines the commandments of men. You leave the commandment of God and hold to the tradition of men.” I pray that we do not abandon the commandment of Abba for vain traditions of men, but that we hold on to the commandment of Abba, and always adhere to His voice first, rightly handling the word of truth.