Here is every instance where it is found in scripture along with the actual Greek (English words that do not appear in the Greek will be in italics):
(KJV)
Matthew 28:1
In the end of the sabbath, as it began to dawn toward the first day of the week [mian sabbaton], came Mary Magdalene and the other Mary to see the sepulchre.
(KJV)
Mark 16:2
And very early in the morning the first day of the week [tes mias sabbaton], they came unto the sepulchre at the rising of the sun.
(KJV)
Luke 24:1
Now upon the first day of the week [mia ton sabbaton], very early in the morning, they came unto the sepulchre, bringing the spices which they had prepared, and certain others with them.
(KJV)
John 20:1
The first day of the week [mia ton sabbaton] cometh Mary Magdalene early, when it was yet dark, unto the sepulchre, and seeth the stone taken away from the sepulchre.
(KJV)
John 20:19
Then the same day at evening, being the first day of the week [te mia ton sabbaton], when the doors were shut where the disciples were assembled for fear of the Jews, came Jesus and stood in the midst, and saith unto them, Peace be unto you.
(KJV)
Acts 20:7
And upon the first day of the week [te mia ton sabbaton], when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
(KJV)
1 Corinthians 16:2
Upon the first day of the week [kata mia sabbaton] let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
Many believe this means "Sun Day", but we find that the word for "day" (emera) does not appear in the Greek.
The word for "first" in every instance in these scriptures is the Greek word mia, which means "one".
It is translated "one" 58 times out of it's 70 occurences (in the KJV) and only 8 times as "first", 7 of which are here (suspiciously) in these "Sun Day" scriptures and once in Titus 3:10.
As we can see, the Greek word for "week" is sabbaton, which literally means "sabbaths". The common Greek word for "first" is protos. Protos emera would have been a better way to communicate "first day", imo.
So if it is not talking about Sun Day, one might ask, then what day is it? The omer count to pentecost is to be completed when seventh sabbaths have passed (Leviticus 23:15). In Leviticus 23:15 of the Greek LXX the word "sabbaths" in the Hebrew is rendered as sabbaton. Pentecost is the next feast after unleavened bread.
Why is this significant? Isn't it interesting to realize that in every instance where we find "first day of the week" in English translations, the feast of unleavened bread or pentecost is the set timing?
In the gospels, the disciples were in the middle of unleavened bread after passover (which is when Christ died).
Consider this:
Matthew
Matthew 26:2
Ye know that after two days is the feast of the passover, and the Son of man is betrayed to be crucified.
...
Matthew 26:17
Now the first day of the feast of unleavened bread the disciples came to Yahshua, saying unto him, Where wilt thou that we prepare for thee to eat the passover?
Mark
Mark 14:1
After two days was the feast of the passover, and of unleavened bread: and the chief priests and the scribes sought how they might take him by craft, and put him to death.
Luke
Luke 22:1
Now the feast of unleavened bread drew nigh, which is called the Passover.
John
John 13:1
Now before the feast of the passover, when Yahshua knew that his hour was come that he should depart out of this world unto the Father, having loved his own which were in the world, he loved them unto the end.
Now regardless of whether or not he died on passover or the day after passover (there are different views on this that we won't get into), it is a must that he rose sometime during unleavened bread (which lasts 7 days, from the 15th to the 21st of Aviv with the passover on the 14th).
During the feast of unleavened bread, the count to pentecost must begin (whether one holds a lunar sabbatarian viewpoint like myself, or believes that the "morrow after the sabbath" in Leviticus is the 15th of Aviv or if you believe in a Saturday sabbath and believe that is the sabbath it was speaking of; but these controversies are also something we won't get into). It is inevitable and mathematically impossible for it not to be unleavened bread when the omer count begins.
When the women and the disciples came to the tomb, it had to be unleavened bread (whether you believe he was in the grave for 3 twenty-four hour periods or not, but again, that is another subject of controversy).
Continuing:
Acts
Acts 20:6
And we sailed away from Philippi after the days of unleavened bread, and came unto them to Troas in five days; where we abode seven days
1 Corinthians
1 Corinthians 5:6
Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?
1 Corinthians 5:7
Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:
1 Corinthians 5:8
Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.
...
1 Corinthians 16:8
But I will tarry at Ephesus until Pentecost.
As far as the 5th chapter of 1 Corinthians reference, I believe he spoke in that manner because it was the time of those feasts and they were actually keeping them, but even if that is not true, it doesn't matter. He mentions pentecost which means it must have been close to pentecost and his mind was set on it (which means the omer count had to have begun). Paul would gather collections from the different congregations and would bring them to Jerusalem (that is what he is speaking of in 1 Corinthians 16:2). That is why he was going to stay in Ephesus until pentecost because when it came, he would go to Jerusalem (according to the command of the law, where all the males were commanded to appear before Yahweh in Jerusalem, which is what was going on in the second chapter of Acts, if you didn't know).
This cannot be coincidence. Not to me. So I judge that all these references to the "first day of the week" is not talking about Sun Day, but is saying "one of the weeks/sabbaths [as the period between one sabbath and another]" during the count to pentecost.
The authors were communicating any of the days of the sabbaton/week when the events mentioned in these scriptures occured (within the 50 days of the count to pentecost).
(KJV)
Matthew 28:1
In the end of the sabbath, as it began to dawn toward the first day of the week [mian sabbaton], came Mary Magdalene and the other Mary to see the sepulchre.
(KJV)
Mark 16:2
And very early in the morning the first day of the week [tes mias sabbaton], they came unto the sepulchre at the rising of the sun.
(KJV)
Luke 24:1
Now upon the first day of the week [mia ton sabbaton], very early in the morning, they came unto the sepulchre, bringing the spices which they had prepared, and certain others with them.
(KJV)
John 20:1
The first day of the week [mia ton sabbaton] cometh Mary Magdalene early, when it was yet dark, unto the sepulchre, and seeth the stone taken away from the sepulchre.
(KJV)
John 20:19
Then the same day at evening, being the first day of the week [te mia ton sabbaton], when the doors were shut where the disciples were assembled for fear of the Jews, came Jesus and stood in the midst, and saith unto them, Peace be unto you.
(KJV)
Acts 20:7
And upon the first day of the week [te mia ton sabbaton], when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
(KJV)
1 Corinthians 16:2
Upon the first day of the week [kata mia sabbaton] let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
Many believe this means "Sun Day", but we find that the word for "day" (emera) does not appear in the Greek.
The word for "first" in every instance in these scriptures is the Greek word mia, which means "one".
It is translated "one" 58 times out of it's 70 occurences (in the KJV) and only 8 times as "first", 7 of which are here (suspiciously) in these "Sun Day" scriptures and once in Titus 3:10.
As we can see, the Greek word for "week" is sabbaton, which literally means "sabbaths". The common Greek word for "first" is protos. Protos emera would have been a better way to communicate "first day", imo.
So if it is not talking about Sun Day, one might ask, then what day is it? The omer count to pentecost is to be completed when seventh sabbaths have passed (Leviticus 23:15). In Leviticus 23:15 of the Greek LXX the word "sabbaths" in the Hebrew is rendered as sabbaton. Pentecost is the next feast after unleavened bread.
Why is this significant? Isn't it interesting to realize that in every instance where we find "first day of the week" in English translations, the feast of unleavened bread or pentecost is the set timing?
In the gospels, the disciples were in the middle of unleavened bread after passover (which is when Christ died).
Consider this:
Matthew
Matthew 26:2
Ye know that after two days is the feast of the passover, and the Son of man is betrayed to be crucified.
...
Matthew 26:17
Now the first day of the feast of unleavened bread the disciples came to Yahshua, saying unto him, Where wilt thou that we prepare for thee to eat the passover?
Mark
Mark 14:1
After two days was the feast of the passover, and of unleavened bread: and the chief priests and the scribes sought how they might take him by craft, and put him to death.
Luke
Luke 22:1
Now the feast of unleavened bread drew nigh, which is called the Passover.
John
John 13:1
Now before the feast of the passover, when Yahshua knew that his hour was come that he should depart out of this world unto the Father, having loved his own which were in the world, he loved them unto the end.
Now regardless of whether or not he died on passover or the day after passover (there are different views on this that we won't get into), it is a must that he rose sometime during unleavened bread (which lasts 7 days, from the 15th to the 21st of Aviv with the passover on the 14th).
During the feast of unleavened bread, the count to pentecost must begin (whether one holds a lunar sabbatarian viewpoint like myself, or believes that the "morrow after the sabbath" in Leviticus is the 15th of Aviv or if you believe in a Saturday sabbath and believe that is the sabbath it was speaking of; but these controversies are also something we won't get into). It is inevitable and mathematically impossible for it not to be unleavened bread when the omer count begins.
When the women and the disciples came to the tomb, it had to be unleavened bread (whether you believe he was in the grave for 3 twenty-four hour periods or not, but again, that is another subject of controversy).
Continuing:
Acts
Acts 20:6
And we sailed away from Philippi after the days of unleavened bread, and came unto them to Troas in five days; where we abode seven days
1 Corinthians
1 Corinthians 5:6
Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?
1 Corinthians 5:7
Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:
1 Corinthians 5:8
Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.
...
1 Corinthians 16:8
But I will tarry at Ephesus until Pentecost.
As far as the 5th chapter of 1 Corinthians reference, I believe he spoke in that manner because it was the time of those feasts and they were actually keeping them, but even if that is not true, it doesn't matter. He mentions pentecost which means it must have been close to pentecost and his mind was set on it (which means the omer count had to have begun). Paul would gather collections from the different congregations and would bring them to Jerusalem (that is what he is speaking of in 1 Corinthians 16:2). That is why he was going to stay in Ephesus until pentecost because when it came, he would go to Jerusalem (according to the command of the law, where all the males were commanded to appear before Yahweh in Jerusalem, which is what was going on in the second chapter of Acts, if you didn't know).
This cannot be coincidence. Not to me. So I judge that all these references to the "first day of the week" is not talking about Sun Day, but is saying "one of the weeks/sabbaths [as the period between one sabbath and another]" during the count to pentecost.
The authors were communicating any of the days of the sabbaton/week when the events mentioned in these scriptures occured (within the 50 days of the count to pentecost).