A LITTLE HISTORY LESSON
Technically, in Jesus' time, the first day of the week would have begun on what we call Saturday night after the sunset and ended with sunset the next night.
So, when we read that the church met on the first day of the week, it could have been any time from about 7-8 pm on Saturday night to 7-8 pm on Sunday night.
According to historians, the Lord's Supper was served in the evening. In fact, it wasn't until the second century that the Lord's supper was added to a formal A.M. worship.
In fact, if we suppose that the first century christians in Rome met on the first day of the week as it appears that they did, we have to understand that Roman slaves did not have Saturday and Sunday off. So, they probably met after the day's work was done on Saturday night (after sunset). These slaves would not have been aforded the opportunity (unless thier owners were understanding christians) to meet on Sunday morning to partake of the Lord's Supper.
The Jews could not have broken thier Sabath rest until sunset, meaning they had a full day's work to catch up from on the first day of the week. Markets would have been open, trade would have been occuring, business would have had to been conducted. First century Jewish christian could not have met until the work day was done or they could have met the night before.
This lends understanding to the I Corinthians passage in which Paul asks the Corithian Church to, "wait for one another." (I Cor 11:33).
So, a church that meets after sunset on Saturday night IS following the example of the first century church and technically, if we follow the definition of a day from the New Testament time, when we offer communion on Sunday nights after sunset, it is no longer the first day of the week.
Technically, you are incorrect.
A LITTLE (REAL) HISTORY LESSON
Though the Jews held that the First day of the week could start at sunset on Saturday, it is common knowledge that the early church defined Sunday as the "Lord's Day". As some of the elders of these congregations actually learned directly from the Apostles, it leaves us with little argument over what the early church considered the "assembly day". Didache, Cyprian, Aristides, Justin Martyr, all discuss this very issue. There are also Roman letters and pamphlets that describe how and when the early Christians met, which again validates Sunday.
The Epistle of Barnabas (c. A.D. 120), discusses how the Lord "abolished" such things as incense, new moons, and sabbaths, because of the "new law of our Lord Jesus Christ" (ANF.I.138). Later, it is affirmed: Wherefore, also, we keep the eighth day with joyfulness, the day also on which Jesus rose again from the dead (I.147).
Justin Martyr (A.D. 140) declared that on the day called Sunday the primitive Christians met for worship. He further stated that this was the day on which Christ was raised from the dead (I.186).
The disciples at Troas were gathered together upon the first day of the week to break bread, i.e., to worship, (Acts 20:7). The specific day of meeting was no accident. Though Paul was anxious to get to Jerusalem (20:16), he waited seven days for the opportunity to assemble with the church.
The saints in Corinth were assembling, and contributing into the church treasury, every first day of the week (1 Cor. 16:2 Greek text; cf. NASB).
THE SABBATH - SOME UNKNOWN FACTS:
The Hebrews actually observed fifty-nine sabbaths each year. In addition, every seventh year was a sabbatical year (Lev. 25:1-4), and each fiftieth year was sabbatical as well (Lev. 25:8-13). The land was to lie uncultivated during these times, and debts were to be cancelled (Dt. 15:2).
In a fifty-year span, the faithful Hebrew, to one degree or another depending upon the specific requirement of the law, would observe 5,830 sabbaths.
LORD'S SUPPER -
As to the Lord's Supper - scholars and historians clearly note that NO ONE knows what time of the day the LS was given during the first two centuries. We know that the group only met once that day, but met for an extended length of time as many members journeyed from the outer countryside. We know they partook of the LS - but not whether it was after breakfast, lunch or dinner. In fact, all we really know is that they shared a "regular" meal afterwards. It wasn't until Tertullian that there is any mention of the LS before "daybreak".
Were you aware that in the first few centuries, the LS was carried to those who were unable to attend? We actually do that today with those that are house bound. Also, some held services on Sunday morning BEFORE daybreak - would this be to aid those who did have to work?
AS TO JEWS AND JEWISH CHRISTIANS -
First Century Jewish Christians were admonished by Jews for NOT observing the Sabbath and for breaking the "law". In fact, many of the early church writings address this issue at some point. They were also admonished by the chruch elders if they treid to abide by such "superstitions" as resting on the Sabbath. It was under the old law and was not to be followed any longer. Ignatius, Justin Martyr and others preached on this very issue. Sunday was to be the Lord's Day. The "old world and old law" was to be put away. As such, they were to "break" the Sabbath.
(I Cor 11:33). Ummm...I don't really think this verse is about the DAY - it has to do with the time of the day they met. No day would have fit everyone's schedule...
THE REAL POINT HERE IS....
Meeting on Saturday night is NOT what was demanded in the Bible nor was it EVER followed by any of the 1st or 2nd century churches for which we have evidences. As for the Sabbath...it concerns me that you keep referring back to it as if it was a law they were to abide by. Jesus specifically told them the old law was no longer. The Sabbath/day of rest was wiped away and was NOT to be a determination in when or how they met.
WHEN WAS THE CHURCH STARTED?
Most importantly, what day was the Church actually started on? We know that day because of the following:
The kingdom of Christ was established on the day of Pentecost (Acts 2:1), which always fell on the morrow after the sabbath (Lev. 23:15-16) - OTHERWISE KNOWN AS SUNDAY. So the church started out meeting for worship on the first day of the week (cf. Acts 2:42).