The 7th day is Sabbath — Sabbath was never changed to Sunday.
Arabic: Sabet
Armenian: Shabat
Bosnian: Subota
Bulgarian: Sabota
Corsican: Sàbatu
Croatian: Subota
Czech: Sobota
Georgian: Sabati
Greek: Savvato
Hebrew: Shabbat
Indonesian: Sabtu
Italian: Sabato
Latin: Sabbatum
Maltese: is-Sibt
Polish: Sobota
Portuguese: Sábado
Romanian: Sambata
Russian: Subbota
Serbian: Subota
Slovak: Sobota
Slovene: Sobota
Somali: Sabti
Spanish: Sabado
Sudanese: Saptu
Ukranian: Subota
Sabbath is the day of worship for the Jews.
Jesus is the Lord of the Sabbath; He brought the New covenant.
That’s why the apostles gathered and worshipped the risen Christ on the day that Christ rose - on Niedziela, dominicus.
In Latin the first day of the week is Dominicus - “the Lord’s Day” and in Polish it’s niedziela = the day of sharing and in Russian it is Воскресенье = resurrection day. You do realize that modern English is quite a few language, right?
An early example of Christians meeting together on a Sunday for the purpose of “breaking bread” and preaching is cited in the New Testament book of Acts (Acts 20:7)
7On the first day of the week, when we met to break bread, Paul was holding a discussion with them; since he intended to leave the next day, he continued speaking until midnight
2nd-century writers such as Justin Martyr attest to the widespread practice of Sunday worship (First Apology, chapter 67
The term “Lord’s” appears in The Teaching of the Twelve Apostles or Didache, a document dated between 70 and 120. Didache 14:1a “But every Lord’s day gather yourselves together, and break bread, and give thanksgiving”
Around 170 AD, Dionysius, Bishop of Corinth, wrote to the Roman Church, “Today we have kept the Lord’s holy day (kyriake hagia hemera), on which we have read your letter.” In the latter half of the 2nd century, the apocryphal Acts of Peter identify Dies Domini (Latin for “Lord’s Day”) as “the next day after the Sabbath,” i.e., Sunday. From the same period of time, the Acts of Paul present St. Paul praying “on the Sabbath as the Lord’s Day (kyriake) drew near.”
Except it wasn't Sunday. It was Saturday night.
The word usually translated "First day of the week" supposedly denoting Sunday by modern Christians is a gross mistranslation of the greek. It is literally this:
(LITV) And on the first of the sabbaths, the disciples having been assembled to break bread, being about to depart on the morrow, Paul reasoned to them. And he continued his speech until midnight.
A proper translation also might be "one of the sabbaths". So the proper way to understand this is that it is one of the sabbaths or perhaps the first of the sabbaths. If "first of the sabbaths" then it's probably denoting the first sabbath that is counted to Pentecost from the days of unleavened bread.
IF it really is the first day of the week then that would have started Saturday after sunset.
Scripture is telling us that one on of the sabbaths (or maybe JUST after the sabbath Saturday night) Paul and the rest of them got together for a meal (breaking bread). They were doing this because Paul was going to leave the next day, Sunday, on a long journey. Paul spoke to almost midnight.
It was either already dark (past sunset on Saturday, or became dark because verse 8 says that the lamps were burning.
After Eutychus falls out of the window and is revived, they break bread (eat) again:
Act 20:11 Now when he had come up, had broken bread and eaten, and talked a long while, even till daybreak, he departed.
So if the argument is that if this was a Sunday night then then they would have been breaking bread and fellowshipping on the 2nd day of the week...Sunday night after sunset. But scripture doesn't say that. Not even close.