In the beginning, the Shabbat was on the seventh day (Genesis 2:1-3)
And during the days of Yeshua HaMashiach, He kept the Shabbat on the seventh day. (Luke 4:16)
Even Shaul, also called Paul, kept the Shabbat of the seventh day. (Acts 17:2)
However, in the 4th century, the Roman empire made their "venerable day of the sun" to be the day to rest. So the Roman churches started to go to church on Sunday, which was the first day of the week.
However, the followers of Yeshua HaMashiach, called The Way or the Nazarene, continued to keep the Shabbat on the seventh day, just like all the other sects of Judaism.
Even though the Protestant Churches left the Roman Catholic in the 16th century, they still retained many of the Roman traditions like going to church on Sunday.
So that's how the Roman Catholic and the Protestants goes to church on Sunday.
However, in Isaiah 66:22-23, it is written that even in the new heaven and the new earth, we will still observe the Shabbat and the Rosh Chodesh.
But these are days of the restoration of the truth and many are keeping the Shabbat on the seventh day.
Shalom Aleichem.
