Do Protestant writers acknowledge the same?

Answer

They do.
NOTE - "IS there no express commandment for observing the first day of the week as Sabbath,
instead of the seventh day?-None whatever. Neither Christ, nor His apostles, nor the first Christians
celebrated the first day of the week instead of the seventh as the Sabbath."-New York Weekly Tribune,
May 24, 1900.
"The Scriptures nowhere call the first day of the week the Sabbath. . . . There is no Scriptural
authority for so doing, nor of course any Scriptural obligation." The Watchman (Baptist).
"The observance of the first instead of the seventh day rests on the testimony of the church, and
the church alone.' -- Hobart Church News, July 2, 1894.
For additional testimonies, see reading on page 146.

What did Jesus say of His attitude toward the law?
If John, therefore, referred to a day of the week, on what day must he have been in the Spirit?
What prophecy spoke of their return from captivity?
When is the resurrection of the righteous to take place?
What is God called in the Scriptures?
What determines whether one is a child of Abraham?
What will the ransomed of the Lord then do?

Questions & Answers are from the book Bible Readings for the Home Circle